The GPD plugin included with 3.1.1 (which is gpd 18.104.22.168) doesn't seem to work with Eclipse 3.2. I've tried the 3.0.10, which seems to be working just fine. You can find that http://sourceforge.net/project/showfiles.php?group_id=70542&package_id=116692&release_id=430212.
The error that you show seems to be some kind of security problem on those directories. Are you sure the user you're running eclipse on has at least "read" access?
Updating the version to 3.0.10 worked.