Unable to take pictures with my Canon Rebel

My Canon EOS Rebel XTi, Ds 126151 camera is not working.

After taking several pictures with this camera, the following error appeared on the screen "there is a problem with CF card, replace." I received the same message after inserting another card.

Both cards seem to work on my computer but not on the camera.

When I tried formatting the cards using the camera, the screen blinks and shows error 99.

Tried turning the camera off and on, removed and reinserted the battery, neither one resolve the problems.

Please help.