Hi,
I'm experiencing the same problem described in https://jira.jboss.org/jira/browse/JBIDE-3573, which has been marked as fixed. I'm using jbossTools-all-win32-3.0.0.GA-N200902101801-H1424. I'm only experiencing the problem for previously-created projects; new projects created via the "new seam project" wizard work fine (as verified in the jira issue). I don't know yet what's different between my old projects and a new project that causes the issue. I can investigate further if it's not immediately obvious to the developers from the stacktrace what the problem is.

Should I open a new jira issue? Should I re-open https://jira.jboss.org/jira/browse/JBIDE-3573?

Thanks for all your hard work on this project!

relevant eclipse log snippet:

!ENTRY org.eclipse.jface 4 2 2009-02-12 12:51:51.750
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
org.eclipse.core.runtime.AssertionFailedException: null argument:
 at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:86)
 at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:74)
 at org.jboss.ide.eclipse.archives.core.model.internal.ArchiveNodeImpl.addChild(ArchiveNodeImpl.java:264)
 at org.jboss.ide.eclipse.archives.core.model.internal.ArchiveNodeImpl.addChild(ArchiveNodeImpl.java:255)
 at org.jboss.ide.eclipse.archives.webtools.archivetypes.EarArchiveType.fillDefaultConfiguration(EarArchiveType.java:105)
 at org.jboss.ide.eclipse.archives.webtools.ui.NewEARAction$EARPreviewPage.addToPackage(NewEARAction.java:90)
 at org.jboss.ide.eclipse.archives.webtools.ui.PreviewPage.pageEntered(PreviewPage.java:104)
 at org.jboss.ide.eclipse.archives.ui.wizards.WizardWithNotification.pageChanged(WizardWithNotification.java:72)
 at org.eclipse.jface.wizard.WizardDialog$5.run(WizardDialog.java:1459)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:37)
 at org.eclipse.core.runtime.Platform.run(Platform.java:880)
 at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:48)
 at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
 at org.eclipse.jface.wizard.WizardDialog.firePageChanged(WizardDialog.java:1457)
 at org.eclipse.jface.wizard.WizardDialog.update(WizardDialog.java:1237)
 at org.eclipse.jface.wizard.WizardDialog.updateForPage(WizardDialog.java:1166)
 at org.eclipse.jface.wizard.WizardDialog.access$2(WizardDialog.java:1139)
 at org.eclipse.jface.wizard.WizardDialog$4.run(WizardDialog.java:1128)
 at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
 at org.eclipse.jface.wizard.WizardDialog.showPage(WizardDialog.java:1126)
 at org.eclipse.jface.wizard.WizardDialog.nextPressed(WizardDialog.java:820)
 at org.eclipse.jface.wizard.WizardDialog.buttonPressed(WizardDialog.java:369)
 at org.eclipse.jface.dialogs.Dialog$2.widgetSelected(Dialog.java:624)
 at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:228)
 at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
 at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
 at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3823)
 at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3422)
 at org.eclipse.jface.window.Window.runEventLoop(Window.java:825)
 at org.eclipse.jface.window.Window.open(Window.java:801)
 at org.jboss.ide.eclipse.archives.webtools.ui.NewEARAction.run(NewEARAction.java:38)
 at org.jboss.ide.eclipse.archives.webtools.ui.NewEARAction.run(NewEARAction.java:43)
 at org.jboss.ide.eclipse.archives.ui.providers.ArchivesActionProvider$ActionWrapper.run(ArchivesActionProvider.java:230)
 at org.eclipse.jface.action.Action.runWithEvent(Action.java:498)
 at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:583)
 at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:500)
 at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
 at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
 at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
 at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3823)
 at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3422)
 at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2384)
 at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2348)
 at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2200)
 at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:495)
 at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)
 at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:490)
 at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
 at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
 at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:193)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:386)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:549)
 at org.eclipse.equinox.launcher.Main.basicRun(Main.java:504)
 at org.eclipse.equinox.launcher.Main.run(Main.java:1236)