When workstations on a Server 2003 domain, report an insufficient memory and/or disk space profile error at login, try this:
http://support.microsoft.com/kb/935649
It also appears to help general memory usage issues. The same settings are listed by Microsoft in Server 2008 for an antivirus issue:
http://support.microsoft.com/kb/973366
This one is from the indefatigable Liz Landry.