It looks like my trusty but aging EOS 5D may be nearing the end of its useful life. I've had the camera for about seven years now and it is starting to malfunction with auto focus and flash sync both failing to work properly. I'll take it over to the Canon shop to see if it can be repaired, but strongly suspect that it will not be worth the cost.
If I do need a new camera, I am inclined to stick with a Canon full frame sensor - either the ID X or 5D III. While the Nikon D800 looks wonderful (and the built in flash has its attractions), given my existing Canon lenses and flash, I don't think it is worth shifting to another brand. Put differently, if I am happy with the 5D, then the 5D III will still be a meaningful step up.