Locked Computer

[Ron]

I would appreciate an explanation for the following
problem.

I was logged onto AOL and left the computer for about 20
minutes. Upon returning the computer was locked and
would not respond to any que. The message window
said, "This computer is in use and can only be unlocked
by then listed my name and the computer number. The
scroll down menu had no other choices. I could not enter
any information. The computer would not shut down with
alt-control-delete or the power switch. To shut down, I
disconnected the power. I have not entered any passwords
or security information.

Thanks for any help you can provide.