automatic lock-out of my user account

I restarted my computer and my account automatically
locked me out. I did not incorrectly input my password.
I used the preset admin account to log in and access
the 'control userpasswords2' command to unlock my
account. Upon restart the account was again locked out.
I logged in with admin again and found out that if I
disable password protect on my account, or if I disabled
administrator privledges from the account then it became
accessible either by not having a password or by not
being locked out respectively. Also, I ran Norton and
McAffee to see if either detected some type of virus, or
trojan but none was found. Anyone have any idea what my
be going on???