This bug was originally marked as duplicate of bug 223309, 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 201212310001)
VM: Java HotSpot(TM) 64-Bit Server VM, 23.6-b04, Java(TM) SE Runtime Environment, 1.7.0_10-b18
OS: Linux

User Comments:
mienamoo: Switching between project groups

sishbi: Reopening a master project

aldobrucale: Closing maven project

GUEST: I was closing a project.

fverhoef: I was closing 2 projects. The directory mentioned in the summary had just been added and commited in svn.

wissenstein: Just gave command "Close required projects".

javydreamercsw: Closing 28 Maven projects

aldobrucale: Closing a project

mienamoo: Switching project groups

pekarna: Switched from current project group (JTexy) to another.

GUEST: close maven project

musilt2: Created Maven CRUD demo sample, added all project to free group, created 2 j2se apps, added them to another free group, and was swithich couple times between those two groups

lhochet: with extra -J-Dorg.openide.filesystems.FileUtil.level=FINE, occured when switching between project groups composed of Maven projects

manikantannaren: Opened 3 maven projects
Edited code
Collapsed all three projects
Closed all three projects

mienamoo: I deleted some source files in one of my open projects and then switched project groups.

kosmonaFFFt: Close maven project...

musilt2: had Maven CRUD demo sample, as one free project group, had 2 j2se apps as second free group, and was switching couple times between those two groups

rptmaestro: Opened a project group

mfriedenhagen: Switching to another group.

GUEST: Switching groups

ionuion: renamed maven project (project name, project artifactId and project folder)

lforet: I was closing maven project




Stacktrace: 
java.lang.IllegalArgumentException: Was not listening to /home/ehugonnet/silver-dev/tools/installer/src/main/resources
   at org.openide.filesystems.FileUtil.removeFileChangeListenerImpl(FileUtil.java:328)
   at org.openide.filesystems.FileUtil.removeRecursiveListener(FileUtil.java:437)
   at org.netbeans.modules.maven.cos.CopyResourcesOnSave.closed(CopyResourcesOnSave.java:111)
   at org.netbeans.modules.maven.ProjectOpenedHookImpl.projectClosed(ProjectOpenedHookImpl.java:289)
   at org.netbeans.spi.project.ui.ProjectOpenedHook$1.projectClosed(ProjectOpenedHook.java:89)
   at org.netbeans.spi.project.ui.support.UILookupMergerSupport$OpenHookImpl.projectClosed(UILookupMergerSupport.java:260)