It seems the light meter indicator in the viewfinder on my Canon 7D underestimates how bright the picture will be. This makes for overexposed photos whenever I use anything other than full manual mode, on the order of 2-3 stops.

Some possible culprits:

• I've used microfiber cloth to clean the camera, including the light sensor. Is any other cleaning necessary?
• Is there any known problem with the hardware or software of these cameras which could account for this?
• Is there any setting which could account for this?