If a module has set nbm.is.global=true (or it's fixed module?) and currently running intance of IDE has no permission to write to installation directory then Plugin Manager show a notification of this fact and recommends to run IDE with administrator role.
*** Bug 203138 has been marked as a duplicate of this bug. ***
Integrated into 'main-golden', will be available in build *201205170950* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Jiri Rechtacek <email@example.com>
Log: #211777: added more tests