sounds like the shutter buffer is disintergrating.
Have a look at the shutter blades - if you see any "black gunk" on them then the only way to fix it is to strip the camera and clean all traces of the gunk from the shutter.
I've fixed many of these in my time - it's a common Canon fault with EOS and some T series shutters
And the winner is....
Originally Posted by Andrew K
How does one go about stripping and cleaning? I only have $12 in this thing, so it would be a great way to learn about camera repair.
Lighter fluid is usually good for removing foam goo from cameras, best applied with a cotton bud in this case.
Cleaning the shutter is only the first step, as the disintegrating bumper is still in there. You'd have to open it up and remove all of it, then install a replacement piece. No, I've never done it. One could, of course, continue to clean the shutter blades as the problem crops up.