Server 2003 Logs in and then immediately out

Hello all,

This is more of an annoyance than a real problem:

I have a standalone Windows 2003 Server (not on a domain). I typically
log into it using a standard user, and only use a user with Admin rights
when I need it.

Occasionally when logging in, the login process will begin and then
immediately log me back out. Logging in again will complete successfully.

- This only seems to happen with a normal user account. The admin
account works fine all the time.

- It seems to occur just after a reboot when logging in for the first
time.

- When it does happen, it only happens once. Logging in a second time
will always work.

- It doesn't coincide with Windows Updates having been applied before
the reboot.

- The server has recently been upgraded (reformat and clean install)
from 2003 R2 Standard 32-bit to 2003 R2 Enterprise x64, and the problem
is still there.

- Nothing in the event log, no errors.


This has me stumped. Any ideas?

Thanks,