java.lang.IllegalArgumentException: Path for project must have only one segment.

Steps to reproduce (similar to http://www.jboss.org/community/docs/DOC-10044, "Installing JBoss Tools from the Update Site" section):

1. get Eclipse Platform Runtime Binary (latest 3.4.2 M build, M20090121-1700)
2. use this script to unpack & run in a clean workspace

#!/bin/bash

eclipse=eclipse-platform-M20090121-1700-linux-gtk.tar.gz
workspace=/home/nboldt/eclipse/workspace-clean
target=/home/nboldt/eclipse/34clean

if [[ $1 ]]; then
echo "Wipe $target/eclipse and $workspace ..."
rm -fr $target/eclipse $workspace
echo "Unpack $eclipse ..."
tar xzf $eclipse
fi

./eclipse/eclipse -clean -showLocation -data $workspace -consolelog -console -vmargs -Xms128M -Xmx256M \
-XX:PermSize=128M -XX:MaxPermSize=256M 2>&1 | tee "eclipse.log.`date`.txt"

3. Help > Software Updates... > Available Software (tab) > Manage Sites... (button)
4. Add these URLs, or, if they're already listed, make sure they're enabled (checked)
o http://download.jboss.org/jbosstools/updates/nightly/trunk/
o http://download.eclipse.org/releases/ganymede/
o http://download.eclipse.org/birt/update-site/2.3/

5. Click OK.
6. Expand the JBoss Tools Update Site and select any or all of the available features listed thereunder.
7. Click Install... then Next and/or Finish. Restart when prompted.

8. New > JBoss JSF/Seam Portlet > Next.

9. See screenshot. You get this in the console:

!ENTRY org.eclipse.jface 4 2 2009-01-23 11:36:21.341
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
java.lang.IllegalArgumentException: Path for project must have only one segment.
at org.eclipse.core.runtime.Assert.isLegal(Assert.java:64)
at org.eclipse.core.internal.resources.WorkspaceRoot.getProject(WorkspaceRoot.java:165)
at org.eclipse.jem.util.emf.workbench.ProjectUtilities.getProject(ProjectUtilities.java:749)
at org.jboss.tools.portlet.ui.internal.wizard.NewJSFPortletClassWizardPage.updateProject(NewJSFPortletClassWizardPage.java:194)
at org.jboss.tools.portlet.ui.internal.wizard.NewJSFPortletClassWizardPage.addProjectNameGroup(NewJSFPortletClassWizardPage.java:188)
at org.jboss.tools.portlet.ui.internal.wizard.NewJSFPortletClassWizardPage.createTopLevelComposite(NewJSFPortletClassWizardPage.java:93)
at org.eclipse.wst.common.frameworks.internal.datamodel.ui.DataModelWizardPage.createControl(DataModelWizardPage.java:103)
at org.eclipse.jface.wizard.WizardDialog.updateForPage(WizardDialog.java:1147)
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.ui.internal.dialogs.NewWizardSelectionPage.advanceToNextPageOrFinish(NewWizardSelectionPage.java:71)
at org.eclipse.ui.internal.dialogs.NewWizardNewPage$1.doubleClick(NewWizardNewPage.java:355)
at org.eclipse.jface.viewers.StructuredViewer$1.run(StructuredViewer.java:799)
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.viewers.StructuredViewer.fireDoubleClick(StructuredViewer.java:797)
at org.eclipse.jface.viewers.AbstractTreeViewer.handleDoubleSelect(AbstractTreeViewer.java:1419)
at org.eclipse.jface.viewers.StructuredViewer$4.widgetDefaultSelected(StructuredViewer.java:1173)
at org.eclipse.jface.util.OpenStrategy.fireDefaultSelectionEvent(OpenStrategy.java:237)
at org.eclipse.jface.util.OpenStrategy.access$0(OpenStrategy.java:234)
...