I downloaded the javaee5 tuturial, unpacked it, and opened the cart-secure
example (under examples/ejb) w/ "open required projects" checked.

This exception was dumped to the console.  I closed the projects and restarted
the IDE.  Reopening the EAR w/ no exception, but right click | Open required
subprojects again caused the same trace.  Probably benign, but I don't think
it's supposed to be happening.

INFORMATIONAL *********** Exception occurred ************ at 2:49 PM on Jul 11, 2006
java.lang.NullPointerException
        at
org.netbeans.modules.javacore.ProgressDisplayer.step(ProgressDisplayer.java:69)
[catch] at
org.netbeans.modules.javacore.internalapi.ProgressSupport.fireProgressListenerStep(ProgressSupport.java:82)
        at
org.netbeans.modules.javacore.internalapi.ProgressSupport.fireProgressListenerStep(ProgressSupport.java:91)
        at
org.netbeans.modules.javacore.jmiimpl.javamodel.UsageFinder$LazyIterator.findNext(UsageFinder.java:349)
        at
org.netbeans.modules.javacore.jmiimpl.javamodel.UsageFinder$LazyIterator.hasNext(UsageFinder.java:367)
        at
org.netbeans.modules.j2ee.metadata.NNMDRListener.getAnnotationUsages(NNMDRListener.java:398)
        at
org.netbeans.modules.j2ee.metadata.NNMDRListener.access$300(NNMDRListener.java:66)
        at
org.netbeans.modules.j2ee.metadata.NNMDRListener$2.run(NNMDRListener.java:119)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:499)
        at
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:932)

You can get the download link for the tutorial from here:
http://java.sun.com/javaee/5/docs/tutorial/doc/JavaEETutorialFront.html