Can not log in as adminstrator in Safe mode

[Cat]

I have Windows XP home edition. After I ran McAfee
antivirus I logged off and I could not log back in from
the Welcome screen. When I try to log on, Windows is
automatically logging me off.
I tried to log in as the Adminstrator in Safe mode but I
experienced the same thing.

Does anybody have any ideea what's going on.
I appreciate your help!

Cat