A friend of mine has a Canon 5DII that has suddenly gone on the blink, Here's what she has to say:
"As soon as I insert a CF card it goes dead. Without the card it comes to life. I tried 3 CF cards and the same thing happens. Can you post this for me on the General Discussion? Maybe someone had that problem and knows what to do. The camera is out of warranty and the nearest Canon service is 200km away. I never had a problem with any of my Canon EOS so it is disappointing that I have a problem with the most expensive one."
I certainly have not heard of this precise problem, but I concur with Cory. It would seem to me that perhaps a pin that should not be grounded is getting connected to ground and causing the camera to sense a problem and not start. First thing I would do is peer into the card slot with a light and magnifier and see if any pins are bent.
Well, that would seem to indicate that there is trouble with the card-to-camera interface circuitry, or perhaps trouble with the mounting of the CF connector to the circuit board in the camera. Those right-angle CF connectors (mechanically the same as PCMCIA) can be susceptible to breakage of solder joints, particularly when mounted to thin circuit boards as they are in this kind of equipment.
I don't have a 5DII, but a few things hit me about the stated operating practices. First of all, my procedure is to shut down camera before removing or inserting CF card. It never occurred to me one could swap CF cards while the camera is live. I think you can scramble the camera's boot procedure. Here's a video for the 5D, but is also supposed to apply to the 5DII. Before anyone sends the camera in for repair, there are some things to try.
Similar thing happened to my old EOS 300 / Rebel. Turned out to be a broken pin. The 5D is probably of better quality than the Rebel but as kirbic said, it's a mechanical factor.
