Yesterday Penelope and I made a trip down to the San Diego Zoo and about half way through our adventures my camera started taking photos on its own in rapid succession while flashing Error 99 on the LCD. I tried pulling the batteries and letting it sit for a while, but that didn't cut it. I looked through my photo archive and I've taken well over 50,000 photos with it since I bought it in February 2005. Looks like I will be without a digital SLR (still have a film SLR body) for a couple of weeks while I get it repaired.
Update After finding someone who had the exact same problem that I did and emailing said person, I found out that I needed to replace my shutter. Canon will do it for $196 which also includes a complete overhaul and cleaning of the camera. It takes 7-10 business days to complete. I am sending it off today.