I was shooting a wedding recently and all of the sudden my camera would not take pictures. I would hit the shutter and nothing would happen. In the eyepiece the flash symbol was flickering. On my 580EXII flash it said TTL flash instead of ETTL. The only way I could get it to work again was if I turned it off, took it off my camera and then set it back up again. I ended up using two cameras that night since I wanted to make sure I could actually take the photo.

Does anyone know what's wrong?
I looked the my flash manual, but couldnt find anything.

I would suspect dirty contacts on either the flash or hot shoe. the TTL mode is a legacy mode reserved for older cameras before they came out with ETTL.

How do I fix that?
Do I just clean them?

I posted about this very thing. Do a quick search and you should find a couple threads about it. Its the wiring in the camera getting messed up by the metal shoe on the 580II.