Jerry, I'll ask a similar question to what I voiced before - because this happens to me once in a while too and I know why - are you metering/focusing off a dark area of the scene like a black tuxedo or dark coat? Again, not to be critical but it is very likely your technique and nothing wrong with the camera.
Have you tried it in Manual mode also with just the flash on Auto?
I have a 5D that will often blow out flash exposures. I've tried every possible exposure setting and it still happens. Not always but enough that I sent it to Canon for repair twice. Problem still exists enough that I replaced it with a 5DII and delegate it to backup or no flash settings.