Q: I have a problem updating my software

Okay, well i have some unusual issue with updating my Mountain Lion 10.8.3 to 10.8.4 via app store.
I was doing the regular update, and everything was just fine, until the download reached about 89%, then it just got frozen so i've waited and after a while it looked like it was completed since there was no download process indicator to find. At leat i guessed so.

Anyways i've tried to exit App Store but it just wouldn't let me because : ''The update is in process'',
So i went to App Store and entered 'Updates' section with showing me again the current update bar with update button.
Ending by clicking the update button again it just went to 'Waiting...' status, but doesn't get any further then that.
Naturally i've tried to exit App Store again but the 'Update is in process' thing was all over me again, so i've also tried to restart and shutdown my system... but i also couldn't do that.

Any suggestions ? Please help it's really annoying, and i really have no clue what is happining. Never dealt with such an issue before...