I added a tool to 9.3 this weekend that will help resolve most cases of this. By popular request I backported it to 9.2.1.9. If you're running an older version of 9.2.1.x you'll have to update to 9.2.1.9 before running the tool.
Code (text):
- mountrw /
- fetch "http://download.freenas.org/errata/fixsid.py" -o /usr/local/bin/fixsid.py
- chmod 755 /usr/local/bin/fixsid.py
- mount -ur /
- rehash
- fixsid.py
