Does anyone here have focusing issues with the new 5D Mark II? I am reeeeeeeeeally frustrated. I am missing some key moments at events and sometimes it won't focus at all! I have to reach up and throw it into manual focus to get what I need and then a few minutes later, I can switch it back and auto-focus works again.
I know you said you already sent in your lens for calibration but you should send the body and lens together. they always advise this. The canon 24-70 is not the best lens to test with either, unless you are certain you have a sharp copy. Its one of the most complained about canon lenses. Do you have a prime lens you can try?
I've also noticed that it has real trouble locking on in backlit situations.
I have an extremely reliable source in NJ that you can send your gear to for serious calibration. Its not cheap but many people I know no longer send their stuff to Canon but to this guy. PM if you want his info.