I got a 7D about a week ago, and i have a strange problem with my external Sigma EF-500 DG Super flash and the 7D.
The problem is that sometimes the Sigma works, sometimes it does not. The flash could be charged and ready but it still won't light up. The flash's light meter checks all the time, but yet the flash still doesn't fire sometimes. When it does, most of the time the pictures are greatly over exposed even with the flash set at +-0 and the shutter speed high and the iso low on the camera. The Sigma's flash shoe horn lock is messed up, but the flash always worked on my XTI and currently works great on an XT body with no issues.
Is there something i missed in the 7D manual? I currently don't have another external flash to test whether it is the body that has a problem.