Interesting, I can not reproduce on Mac OS X 10.4 with the latest build from http://deadlock.netbeans.org/hudson/job/trunk/.

Are you using any modules from the update center? Can you please send your full IDE log? 

Also, can you please try with the latest build, and with a clean user directory?

Afraid that was the complete log... I was never able to work out what the Java 6 class was.

I have the J2SE NetBeans 6.1 beta with developer collaboration, J2EE, Web Applications and GWT4NB plugins.

Will try with latest build soon.

Ok, I reproduced this with the nightly 200804011203 on OS X 1.5 Intel running latest Java 5 (the official latest Java release).

Sorry, the stack trace doesn't point at the offending class file... however, I did some command line scripting to inspect the version numbers of all the class 
files, and all files were one of versions 45.3, 46.0, 47.0, 48.0, 49.0 or 50.0 except for javax/servlet/jsp/jstl/core/ConditionalTagSupport.class which is 
coming up as having the magic number of a PalmOS application! WTF? This file seems to be part of modules/ext/jstl.jar

java.lang.UnsupportedClassVersionError: Bad version number in .class file
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:675)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:280)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
	at org.netbeans.ProxyClassLoader.loadClass(ProxyClassLoader.java:213)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:374)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:242)
	at sun.misc.Service$LazyIterator.next(Service.java:271)
	at javax.script.ScriptEngineManager.initEngines(ScriptEngineManager.java:127)
	at javax.script.ScriptEngineManager.access$000(ScriptEngineManager.java:55)
	at javax.script.ScriptEngineManager$1.run(ScriptEngineManager.java:98)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.script.ScriptEngineManager.init(ScriptEngineManager.java:96)
	at javax.script.ScriptEngineManager.<init>(ScriptEngineManager.java:69)
	at org.netbeans.modules.templates.ScriptingCreateFromTemplateHandler.engine(ScriptingCreateFromTemplateHandler.java:125)
	at org.netbeans.modules.templates.ScriptingCreateFromTemplateHandler.accept(ScriptingCreateFromTemplateHandler.java:67)
	at org.openide.loaders.MultiDataObject.handleCreateFromTemplate(MultiDataObject.java:694)
	at org.openide.loaders.DataObject$CreateAction.run(DataObject.java:1251)
	at org.openide.loaders.DataObjectPool$1WrapAtomicAction.run(DataObjectPool.java:238)
	at org.openide.filesystems.EventControl.runAtomicAction(EventControl.java:120)
	at org.openide.filesystems.FileSystem.runAtomicAction(FileSystem.java:499)
	at org.openide.loaders.DataObjectPool.runAtomicAction(DataObjectPool.java:250)
	at org.openide.loaders.DataObject.invokeAtomicAction(DataObject.java:865)
	at org.openide.loaders.DataObject.createFromTemplate(DataObject.java:797)
	at org.openide.loaders.DataObject.createFromTemplate(DataObject.java:777)
	at org.netbeans.modules.web.wizards.PageIterator.instantiate(PageIterator.java:222)
	at org.openide.loaders.TemplateWizard.handleInstantiate(TemplateWizard.java:595)
	at org.openide.loaders.TemplateWizard.instantiateNewObjects(TemplateWizard.java:416)
	at org.openide.loaders.TemplateWizardIterImpl.instantiate(TemplateWizardIterImpl.java:248)
	at org.openide.loaders.TemplateWizardIteratorWrapper.instantiate(TemplateWizardIteratorWrapper.java:161)
	at org.openide.WizardDescriptor.callInstantiateOpen(WizardDescriptor.java:1387)
	at org.openide.WizardDescriptor.callInstantiate(WizardDescriptor.java:1341)
	at org.openide.WizardDescriptor.access$1600(WizardDescriptor.java:119)
	at org.openide.WizardDescriptor$Listener$2$1.run(WizardDescriptor.java:1908)
	at org.openide.WizardDescriptor$Listener$2.run(WizardDescriptor.java:1957)
	at org.openide.WizardDescriptor.lazyValidate(WizardDescriptor.java:1316)
	at org.openide.WizardDescriptor.access$1200(WizardDescriptor.java:119)
	at org.openide.WizardDescriptor$Listener.actionPerformed(WizardDescriptor.java:1964)
Caused: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:585)
	at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:449)
Caused: java.lang.reflect.UndeclaredThrowableException
	at $Proxy24.actionPerformed(Unknown Source)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1882)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2202)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
	at java.awt.Component.processMouseEvent(Component.java:5602)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3135)
	at java.awt.Component.processEvent(Component.java:5367)
	at java.awt.Container.processEvent(Container.java:2010)
	at java.awt.Component.dispatchEventImpl(Component.java:4068)
	at java.awt.Container.dispatchEventImpl(Container.java:2068)
	at java.awt.Component.dispatchEvent(Component.java:3903)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4256)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3936)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3866)
	at java.awt.Container.dispatchEventImpl(Container.java:2054)
	at java.awt.Window.dispatchEventImpl(Window.java:1791)
	at java.awt.Component.dispatchEvent(Component.java:3903)
[catch] at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
	at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:180)
	at java.awt.Dialog$1.run(Dialog.java:535)
	at java.awt.Dialog$2.run(Dialog.java:563)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.awt.Dialog.show(Dialog.java:561)
	at org.netbeans.core.windows.services.NbPresenter.superShow(NbPresenter.java:835)
	at org.netbeans.core.windows.services.NbPresenter.doShow(NbPresenter.java:869)
	at org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:857)
	at org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:108)
	at org.openide.util.Mutex.doEventAccess(Mutex.java:1355)
	at org.openide.util.Mutex.readAccess(Mutex.java:268)
	at org.netbeans.core.windows.services.NbPresenter.show(NbPresenter.java:842)
	at java.awt.Component.show(Component.java:1302)
	at java.awt.Component.setVisible(Component.java:1255)
	at org.openide.loaders.TemplateWizard.instantiateImpl(TemplateWizard.java:502)
	at org.openide.loaders.TemplateWizard.instantiate(TemplateWizard.java:381)
	at org.netbeans.modules.project.ui.actions.NewFile.doPerform(NewFile.java:153)
	at org.netbeans.modules.project.ui.actions.NewFile.access$200(NewFile.java:84)
	at org.netbeans.modules.project.ui.actions.NewFile$PopupListener.actionPerformed(NewFile.java:348)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1882)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2202)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:334)
	at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1051)
	at apple.laf.CUIAquaMenuItem.doClick(CUIAquaMenuItem.java:119)
	at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1092)
	at java.awt.Component.processMouseEvent(Component.java:5602)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3135)
	at java.awt.Component.processEvent(Component.java:5367)
	at java.awt.Container.processEvent(Container.java:2010)
	at java.awt.Component.dispatchEventImpl(Component.java:4068)
	at java.awt.Container.dispatchEventImpl(Container.java:2068)
	at java.awt.Component.dispatchEvent(Component.java:3903)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4256)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3936)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3866)
	at java.awt.Container.dispatchEventImpl(Container.java:2054)
	at java.awt.Window.dispatchEventImpl(Window.java:1791)
	at java.awt.Component.dispatchEvent(Component.java:3903)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
	at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:184)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:176)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)

Is it reproducible with clean user dir and fresh build? What are the classes with 50.0 class version?

From the stack trace - there is probably some engine on classpath compiled with java6. Maybe it is not directly related
to web component...

Thanks, P.

Can't reproduce it with mentioned build. Because this issue has no duplicate I'd guess that some extra module is the cause.

Can you try fresh netbeans using clean userdir?

On a clean directory, I can't reproduce this bug... it must be something to do with my local plugins. It even works if I click to import my 6.0 settings.

This could be related (or even duplicate if the reporter will confirm that) to the issue 129227.

well spotted phejl! This is a dupe, I get exactly the same thing when creating a J2SE project. I am not able to mark this as a duplicate though, can you do that 
please?

Reopening to mark it as duplicate.

*** This issue has been marked as a duplicate of 129227 ***