Canon 20d, mirror constantly setting

preliminary reviews of various forums indicate that this is a shutter-lock issue, requiring the whole shutter assembly to be replaced.
I just sent mine in for repairs for the same issue, but they haven't diagnosed it yet.
It seems that the going rate is around 200$ for a replacement assembly, though some have claimed it has costed as much as $350.

If you take the lens off, pop the battery in, you'll notice the shutter isn't actuating, only the mirror is flipping up and down.