After disabling several modules, I disabled the
form editor module, and got the exception below,
using NB 3.4 beta 2.

Note - ignore the core and java patches in the log
file - the core patch only affects NbTheme.java
and the java module patch adds a couple components
to the import wizard - neither are likely to have
anything to do with this.

Will attach log file.

Annotation: Exception occurred in Request Processor
java.lang.IllegalStateException: Call to change()
while stopped
        at
org.netbeans.core.modules.ChangeFirer.change(ChangeFirer.java:54)
        at
org.netbeans.core.modules.ModuleManager.disable(ModuleManager.java:732)
        at
org.netbeans.core.modules.ModuleList$Listener.stepDisable(ModuleList.java:1886)
        at
org.netbeans.core.modules.ModuleList$Listener.access$2000(ModuleList.java:1499)
        at
org.netbeans.core.modules.ModuleList$5.run(ModuleList.java:1717)
        at
org.openide.filesystems.EventControl.runAtomicAction(EventControl.java:89)
        at
org.openide.filesystems.FileSystem.runAtomicAction(FileSystem.java:416)
        at
org.netbeans.core.modules.ModuleList$Listener.run(ModuleList.java:1696)
        at org.openide.util.Task.run(Task.java:136)
[catch] at
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:599)