So here is my situation:

Currently logged onto my PC at work... WIndows boots, I choose the correct domain, enter my credentials and bam I'm in.

When i leave my workstation, ctrl+alt+del to lock the desktop. Upon return and bring up the login thing as usual it says that only I, or Admin can unlock the desktop. I enter my creds... it won't recognize them. A person who knows the Admin creds come down, it won't recognize them either.

Any clues to why this is happening?

I can always reboot and relog back in, but that's just retarded.