Hey Niko, I have had similar problems where my camera would be stuck with "BUSY"flashing and some error code and a couple of times stuck saying loading with all buttons frozen. I cant exactly remember what I did but I did lots of stuff like battery in and out and disconnect and reconnecting to pc and some how it came good. Even try a new memory card as it may be stuffed. Just a guess.
But my problems were caused by the pc crashing whilst in the middle of a shoot connected to the camera.
If all else fails it may be time to get a 6D.
