Could you please provide some more information like:
o what build do you use?
o do you use the default (bundled) tomcat server or an external one?
o have you tried to start the IDE with clear userdir?
o ...

Thanks a lot!
Marek

This exception always appears after Q-Build 200403040727 
instalation, when starting bundled tomcat server.

Don't know if there is any relation, but tomcat server properties 
(in runtime tab) shows an empty Home Directory, and when I try to 
set it this exceptions occurs:
java.lang.NullPointerException
	at 
org.netbeans.modules.tomcat5.nodes.TomcatInstanceNode.getHome
(TomcatInstanceNode.java:199)
	at 
org.netbeans.modules.tomcat5.nodes.TomcatInstanceNode.access$900
(TomcatInstanceNode.java:43)
	at 
org.netbeans.modules.tomcat5.nodes.TomcatInstanceNode$5.getValue
(TomcatInstanceNode.java:355)
	at 
org.openide.explorer.propertysheet.PropUtils.updateEdFromProp
(PropUtils.java:915)
	at 
org.openide.explorer.propertysheet.PropUtils.getPropertyEditor
(PropUtils.java:882)
	at 
org.openide.explorer.propertysheet.SheetTable.onCustomEditorButton
(SheetTable.java:638)
	at 
org.openide.explorer.propertysheet.SheetTable.processMouseEvent
(SheetTable.java:555)
	at java.awt.Component.processEvent(Component.java:4897)
	at java.awt.Container.processEvent(Container.java:1569)
	at java.awt.Component.dispatchEventImpl(Component.java:3615)
	at java.awt.Container.dispatchEventImpl(Container.java:1627)
	at java.awt.Component.dispatchEvent(Component.java:3477)
	at java.awt.LightweightDispatcher.retargetMouseEvent
(Container.java:3483)
	at java.awt.LightweightDispatcher.processMouseEvent
(Container.java:3195)
	at java.awt.LightweightDispatcher.dispatchEvent
(Container.java:3128)
	at java.awt.Container.dispatchEventImpl(Container.java:1613)
	at java.awt.Window.dispatchEventImpl(Window.java:1606)
	at java.awt.Component.dispatchEvent(Component.java:3477)
[catch] at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy
(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy
(EventDispatchThread.java:151)
	at java.awt.EventDispatchThread.pumpEvents
(EventDispatchThread.java:145)
	at java.awt.EventDispatchThread.pumpEvents
(EventDispatchThread.java:137)
	at java.awt.EventDispatchThread.run
(EventDispatchThread.java:100)

My user dir is the one created by previous Q-build 200402251620.

Cleaning my user dir seems to solve the problem, but this way I 
loose some netbeans settings.

thanks

Seems to be connected to 5.0.18 -> 5.0.19 upgrade. Please have a look
whether you don't have directory jakarta-tomcat-5.0.18_base in your
userdir.

Still, could we make some fix which would handle this scenario more
gracefully, at least in the trunk?

Why should we support importing or userdir reusing from older build
which is not officially supported? Maybe I do not fully understand you
comment Petre.

Because many users have hit this problem, especially the users in the
CAT program. We've had many bug reports caused by this. 

Right, even if this applies only for users who doesn't user official
releases and do imports from various trunk builds or Qbuilds. We can
also send and additional info to the NetCAT users when they are asked
to evaluate a new build.

Maybe worth fixing in trunk but in my opinion not in release36.
Although annoying this is not a P2 since this upgrade is not
officially supported.

But I agree with Petr J that some help/advice for users should be
provided. A simple workaround for users of daily builds / Q-builds
should be to remove the tomcat instance and add it again by browsing
the correct home dir (in netbeans installation folder) and base dir
(in user dir). 

Note that in general it is strongly recomended to use different
userdir for testing of builds that are not final releases. Using a
clean userdir would help in this case.

*** This issue has been marked as a duplicate of 40659 ***