I solved this annoying issue
It was an Open Directory issue. If you have upgraded clients to 10.7 or 10.8 from 10.6, the OD Master passwords are incompatible with 10.7 or 10.8.
The fix is simple.
1. Stop AFP file shares
2. Export Users, Groups and Computers from Workgroup Manager then quit the the Workgroup Manager
3. Demote the OD Master to Standalone
4. Promote the Standalone OD to a Master OD,
5. Reimport the Users, Groups and Computers back into Workgroup Manager
6. Reset all passwords and home folders
7. Rebind all clients computers
I hope this helps someone.