This bug was originally marked as duplicate of bug 178174, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.

Build: NetBeans IDE Dev (Build 100323-858c0e4f0c65)
VM: Java HotSpot(TM) 64-Bit Server VM, 14.3-b01, Java(TM) SE Runtime Environment, 1.6.0_17-b04
OS: Windows 7

User Comments:
GUEST: Creating/deleting a project group

mschovanek: Closing the opc-ejb project. See issue #178176 (attachement #92165).

GUEST: closing a project

tk_fhd_aui: Raised after clicking on directory in open project dialog for master project for new project group.

evillive: 1. Create standart Java EE 5 (Tomcat 6.0) Web Application. Add JSF 2.0 support.
2. Close created project

jsedek: closing a simple java application with 3 java classes

GUEST: Creating a Zend Framework Project  - On the page where you select which PHP Framework you want to use for this project

javydreamercsw: Deleted a project still referenced by other (still opened)

ingoreinhart: - no project open
- open project via open project dialog
- close the project

javydreamercsw: Closing a project

GUEST: changed project group

fvogler: Close two freeform projects.

pjiricka: I recently closed the project the exception is complaining about, then I tried to open a file in another project, at which point the exception occurred.

jrechtacek: While closing projects

jsedek: invoked run web application and IAE was thrown few seconds after

ovrabec: just changed a project group

sunflower: NetBeans-JavaFX-Soma: #121

I closed some JavaFX applications and got the exception IllegalArgumentException

charlweed: Opening java.hints project.

jsedek: creating new web java ee5 application on jboss

jglick: Closed NBM project.




Stacktrace: 
java.lang.IllegalArgumentException: org.openide.filesystems.DeepListener@4feb03b7 was not listening to Q:\projects\3rdparty\netbeans\main\java.source\src; only to [Q:\projects\3rdparty\netbeans\main\editor.settings.storage\src, Q:\projects\3rdparty\netbeans\main\editor.settings\build\classes-generated, Q:\projects\3rdparty\netbeans\main\o.apache.tools.ant.module\src, Q:\projects\3rdparty\netbeans\main\openide.util\test\unit\src, Q:\projects\3rdparty\netbeans\main\editor.fold\src, Q:\projects\3rdparty\netbeans\main\editor.codetemplates\src, Q:\projects\3rdparty\netbeans\main\lexer\build\classes-generated, Q:\projects\3rdparty\netbeans\main\spi.quicksearch\src, Q:\projects\3rdparty\netbeans\main\spi.quicksearch\build\classes-generated, Q:\projects\3rdparty\netbeans\main\editor.lib2\build\classes-generated, Q:\projects\3rdparty\netbeans\main\projectuiapi\src, Q:\projects\3rdparty\netbeans\main\editor.lib2\src, Q:\projects\3rdparty\netbeans\main\options.keymap\src, Q:\projects\3rdparty\netbeans\main\spi.tasklist\
   at org.openide.filesystems.FileUtil.removeFileChangeListenerImpl(FileUtil.java:297)
   at org.openide.filesystems.FileUtil.removeRecursiveListener(FileUtil.java:349)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsListeners.remove(RepositoryUpdater.java:3863)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.notifyRootsRemoved(RepositoryUpdater.java:2892)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.getDone(RepositoryUpdater.java:2832)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doTheWork(RepositoryUpdater.java:1926)