This issue frsutrated me so badly, as I had an essentially worthless body on my hands, that I started researching how to roll back the update. In the process of finding out that such a manuever is essentially impossible for the consumer, I hooked the camera to my laptop and realized through EOS Utilities that I only had Firmware update 2.0.0. With nothing better to do, I went ahead and installed 2.0.3 and it appears to have solved my problem. Otherwise I had every symptom the OP was experiencing, to such a bad extent that I couldn't use the camera. I've shot 120000+ images with the body, so to have it just go kaput after a firmware update is totally unacceptable and an obvious sign that the update was the clear culprit. Canon needs to figure this one out in a big hurry.
You might try reinstalling the update and pray that solves the issue.