Originally Posted by
djzuk
I've only had something slightly similar happen to my 20D a few times. Two of the times it was when using AI Servo and it gave me an error... forget what number it gave me (maybe Err 20 or Err 99? Not sure). I think I just took out the battery and put it back in and it worked. The other time I think it was just because I'd run out of battery or space on my memory card or something like that. Maybe you should try reformatting your memory card. I'm no expert on this by any means, but that might be the problem.
Hope this helps.
Derrick