Last night I was shooting a nightclub when my 1D started acting up, the autofocus on my 50 1.8 seemed to lock up and as soon as I would hit the shutter it'd lock up half way and give me an error message. I couldn't even focus it manually, and the drive mode I had selected was pulsating on the LCD screen (the same way your battery meter pulses when it's about to run out). I originally blamed it on the battery and shut the camera off and then restarted again, but when it happened again more frequently I panicked and stopped shooting.
I took my gear to the car, changed lenses to my wide angle zoom and it seemed to work fine. With the 50, before I stopped shooting, it could barely get a photo in before giving me an error message; but with the other lens I shot nearly a 50 shot burst and it was working fine. I kept shooting and had no problems, even went back to the 50 for a few shots and it worked fine.
Is this a sign of my autofocus on the 50mm dying or is it my shutter? My camera IS old, it's the 1D classic. But in the year I've owned it it's never given me any problems. I'm worried as hell, I just started getting steady gigs 
