NetBeans Build:NB dev (200805030003)
Appserver Build
:glassfish-installer-v2.1-b31-windows(https://glassfish.dev.java.net/public/alldownloads.html#Promoted_binary_builds)

JDK Build:jdk1.5.0_13

Steps to reproduce:
1.Install NB and glassfish-installer-v2.1.
2.Start IDE.
3.Right click on the server node select GlassFish V2 and give platform location for glassfish-installer-v2.1.
4.Remove the glassfish-installer-v2.1 location from the dialog window "Platform folder location" and then give same
location for glassfish-installer-v2.1 by selecting the BROWSE button.

After giving proper location of the GlassFish V2.1, generating exception message as:

java.lang.NullPointerException
	at org.netbeans.modules.j2ee.sun.ide.j2ee.ui.AddDomainPlatformPanel.isValid(AddDomainPlatformPanel.java:228)
	at org.openide.WizardDescriptor.updateStateOpen(WizardDescriptor.java:750)
	at org.openide.WizardDescriptor.updateState(WizardDescriptor.java:720)
	at org.netbeans.modules.server.ui.wizard.AddServerInstanceWizard.updateState(AddServerInstanceWizard.java:142)
	at org.openide.WizardDescriptor$Listener.stateChanged(WizardDescriptor.java:1838)
	at org.openide.util.WeakListenerImpl$Change.stateChanged(WeakListenerImpl.java:319)
	at org.netbeans.modules.j2ee.sun.ide.j2ee.ui.AddDomainPlatformPanel.fireChangeEvent(AddDomainPlatformPanel.java:366)
	at org.netbeans.modules.j2ee.sun.ide.j2ee.ui.AddDomainPlatformPanel.stateChanged(AddDomainPlatformPanel.java:395)
[catch] at
org.netbeans.modules.j2ee.sun.ide.j2ee.ui.AddInstanceVisualPlatformPanel$3$1.run(AddInstanceVisualPlatformPanel.java:193)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
	at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:153)
	at java.awt.Dialog$1.run(Dialog.java:535)
	at java.awt.Dialog$2.run(Dialog.java:563)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.awt.Dialog.show(Dialog.java:561)
	at org.netbeans.core.windows.services.NbPresenter.superShow(NbPresenter.java:835)
	at org.netbeans.core.windows.services.NbPresenter.doShow(NbPresenter.java:869)
	at org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:857)
	at org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:108)
	at org.openide.util.Mutex.doEventAccess(Mutex.java:1355)
	at org.openide.util.Mutex.readAccess(Mutex.java:268)
	at org.netbeans.core.windows.services.NbPresenter.show(NbPresenter.java:842)
	at java.awt.Component.show(Component.java:1302)
	at java.awt.Component.setVisible(Component.java:1255)
	at
org.netbeans.modules.server.ui.wizard.AddServerInstanceWizard.showAddServerInstanceWizard(AddServerInstanceWizard.java:115)
	at org.netbeans.modules.server.ui.node.AddServerInstanceAction.performAction(AddServerInstanceAction.java:58)
	at org.openide.util.actions.NodeAction$DelegateAction$1.run(NodeAction.java:581)
	at org.netbeans.modules.openide.util.ActionsBridge.doPerformAction(ActionsBridge.java:77)
	at org.openide.util.actions.NodeAction$DelegateAction.actionPerformed(NodeAction.java:577)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:302)
	at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1051)
	at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1092)
	at java.awt.Component.processMouseEvent(Component.java:5517)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3135)
	at java.awt.Component.processEvent(Component.java:5282)
	at java.awt.Container.processEvent(Container.java:1966)
	at java.awt.Component.dispatchEventImpl(Component.java:3984)
	at java.awt.Container.dispatchEventImpl(Container.java:2024)
	at java.awt.Component.dispatchEvent(Component.java:3819)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
	at java.awt.Container.dispatchEventImpl(Container.java:2010)
	at java.awt.Window.dispatchEventImpl(Window.java:1791)
	at java.awt.Component.dispatchEvent(Component.java:3819)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
	at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)

If we give platform location for other installed appservers , there is no exception message.