steps to reproduce:

- user "ADMIN" installs shared extension "ScriptDispatch.oxt" from:
  http://www.openoffice.org/issues/show_bug.cgi?id=98990

  C:\Programme\OOo-dev 3\program>unopkg add c:\ScriptDispatch.oxt 
    --shared --verbose
  [...]
  [Enter "yes" or "no"]:yes
   Copying: ScriptDispatch.oxt
    Enabling: ScriptDispatch.oxt
    Enabling: ScriptDispatch
  unopkg done.

- start oo
- check with "StartScriptdispatch.odt" from 
  http://www.openoffice.org/issues/show_bug.cgi?id=98990
- close oo

- change to user "USER" (a user without admin privileges)
- start oo
- check with "StartScriptdispatch.odt"
- close oo
- uninstall extension:
  C:\Programme\OOo-dev 3\program>unopkg remove 
   org.test.java.scriptdispatch --shared --verbose
   Disabling: ScriptDispatch.oxt
   Disabling: ScriptDispatch
  unopkg done.

  btw: User "USER" can not uninstall via "Tools - Extension Manager...",
          cause "Remove" button is disabled ...
  
- user "USER"'s "shared-extension-desc.xml" will now look like:

  <?xml version="1.0" encoding="UTF-8"?>
  <unopackages xmlns:unopackages="unopackages.dtd">
     <language value="Java"/>
  </unopackages>

  but the extension is not removed from:
  C:\Programme\OOo-dev 3\share\uno_packages\cache
 
- user "ADMIN" can still use the shared extension while user "USER" can not.

- if user "USER" tries to reinstall the extension he will fail:
  ERROR: You need write permissions to install a shared extension!
       Cause: void
  unopkg failed.

is this behaviour intended ?

imho the root cause for the problem is, that the "shared-extension-desc.xml"
is located inside the user directory "3\user\Scripts\". the content is redundant.

In OO 3.2 the file was in:
"C:\Program Files\OpenOffice.org\Basis\share\Scripts\unopkg-desc.xml"
and so changing the file failed without write permissions.