Not enough storage is available to process this command

[J]

I had this issue twice on two different computers.

Network: AD 2003
Desktops: Win XP Sp2 w/ updates thru 11/15/06

Issue
User connects over VPN to remote desktop. The user gets an unknown error
message. They are unable to login to RDC. They come into they office the next
day to login. The computer is locked with their credentials from a previous
login. When they attempt to login, they receive the error message "Not enough
storage is available to process this command".

Current Resolutions
1. The first computer I was able to login as admin and restart.
2. The second computer gave admin the same message. I had to press the power
button which initiated a shutdown.

Any suggestions?