Windows 2003 Domain with XP-SP3 clients.
Before we installed SP3 the "My Documents" folder pointed to seperate network shares for each user. \\servername\homes$\%username%
After SP3 was deployed we found they all pointed to one users folder (which they had no access to!)
Rolling back SP3 has cured the problem.
Thought it worth giving you a "Heads up" on it.