Think System is corrupted.
Basically you create another admin account, which really is far too easy to do, but here we go:
Maybe this fix bug there...if not works, only way is reinstall entire OSX.
(Remove all quotes before typing the commands I put here)
1) Start up in Single-User mode by type F8 on startup and typing -S
2) Type "/sbin/fsck -y", hit return, then type "/sbin/mount -wu /"
3) Once you have the prompt again type "cd /var/db/"
4) The prompt will change slightly. Then type "ls" and verify that somewhere in the table of items there is the file: ".AppleSetupDone"
5) Making sure that this file is there, then you can delete it by typing "rm ./.AppleSetupDone" or move it to the root of your hard drive for safekeeping by typing "mv ./.AppleSetupDone /"
6) Once it is no longer in place, type "reboot" and the computer will restart...and the first-run video will play and prompt you to register. You don't have to fill any of this in, you can just press Apple(ALT)+Q, confirm the dialog, and you'll be presented with a page where you set up a new admin account. Put in whatever you want, log in, and you can change the password on your main account.