We have a Canon Rebel XT, about 2 years old, which is now consistantly showing these symptoms: Start by removing and re-inserting main battery. Shoot 4 shots. Shooting a fifth shot results in "Error 99" message. Turn camera off/on dispels message. Taking another shot results in immediate "Error 99" message. Remove and re- insert of main battery allows you to shoot 4 more shots, but fifth shot yields "Error 99". The camera is out of warranty, and I *think* has had about 6200 shots taken. We've tried shooting with different lens, without lens, cleaning contacts, without card. Have tried shooting with lens off with mirror lock-up, to have a look at the shutter leafs, they look flat and uniform. The camera has the latest firmware. Any ideas?