580EX overexposing in Manual on 5D

This is a recent issue, I've never had a problem before a couple of weeks ago but my 580EX seems to be overexposing by roughly 1/3 stop when the camera is in manual mode using ETTL on my 5D. If this was ALWAYS the case I wouldn't be as concerned since I could just leave it -1/3 but since it's a new development I am wondering. In auto mode it seems to be working fine. I tried it on both the 5D and 30D and it is only a problem on the 5D, so I'm assuming it's actually the camera.

I have cleaned the contact points with no change. The hot shoe does have a very small amount of play, but it has since I've owned the camera.

Any other suggestions?

By "auto mode", do you mean something like Tv or Av, or are you referring to the green box?

Disregard... it was the loose hot shoe. Found a tutorial to fix it, and problem is solved.