A project exported from subversion into JBoss DevStudio cannot be opened. The Eclipse log shows NullPointerException, either at startup or later. Here is the one at startup:

!ENTRY org.eclipse.core.jobs 4 2 2008-05-23 15:25:55.615
!MESSAGE An internal error occurred during: "Initializing Java Tooling".
!STACK 0
java.lang.NullPointerException
at org.jboss.ide.eclipse.as.classpath.core.ejb3.EJB3ClasspathContainer.getClasspathEntries(EJB3ClasspathContainer.java:113)
at org.eclipse.jdt.internal.core.JavaModelManager.containerPutIfInitializingWithSameEntries(JavaModelManager.java:547)
at org.eclipse.jdt.internal.core.SetContainerOperation.executeOperation(SetContainerOperation.java:49)
at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:720)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1797)
....

Speculation on what went wrong: The .classpath of the project has a Windows-Nature Absolute Path (a Bad Thing in our mixed environment), somehow created on an Eclipse with manually loaded-in JBoss Tools:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
<classpathentry kind="src" path="src"/>
<classpathentry kind="src" path="test"/>
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
<classpathentry combineaccessrules="false" kind="src" path="/jb_seam_demox-ejb"/>
<classpathentry kind="lib" path="D:/jboss-seam-2.0.0.GA/lib/testng.jar"/>
<classpathentry kind="con" path="org.jboss.ide.eclipse.as.classpath.core.ejb3.classpathContainer/JBoss 4.2 Server"/>
<classpathentry kind="output" path="bin"/>
</classpath>