It's time to upgrade my trusty 10d anyway, but hopefully I can solve this problem so the camera is still usable as a backup.

I shoot almost exclusively manual, but a few weeks ago, the light meter kept trying to tell me that I was underexposing by about 2 steps with settings I know should be spot on. Switching the camera to av or tv confirmed this, as every shot was WAY overexposed. I have reset the camera to default a few times now still have the problem.

Does this sound familiar to anyone else?

How's your exposure compensation setting?

i agree with beeman.You can adjust exposure compensation with the big dial on the body without even knowing it..Start by looking there first.
-Jim

Believe me - I have checked the exposure compensation and I know that that is not the problem. The camera overexposes with the exposure compensation set to 0. I have actually made it kind of work for me by setting the compensation to underexpose by 2 stops.

Also, it doesn't seem to consistantly overexpose by 2 stops, but that seems to be the average.

Do you get the same results regardless of what lens you use? I had my 10D for several years and nothing like this.

Yes, I have tested it on four different lenses, with the same effect. This camera has seen a lot of use and this is the first time I've run into any problem with it.

Did the problem just start out of the blue? As in yesterday it was fine, this morning it was toast.

Considering the price of repairs and the price of used 30D's on the "Buy & Sell" forum, it may be an excellent "excuse" for an upgrade; maybe even go for a 1D.

Try the different metering modes to see if there's any difference in exposure.

Try a master reset on the body. Clear all the settings and C.fn.'s. Happened to me once a few years ago with my 10D, and that did the trick.