Back luck Gerry.
I'm also having shutter problems with my 40D, it keeps on sticking. As I've also damaged my rear screen, having heard of your problems I doubt I'd get it done under warranty.
If I were you I'd argue against their decision as much as you possibly can. If your pretty certain it's not been out in anything worse than an odd drop of rain I can't see how that can ruin the shutter.
It certainly is annoying when it happens on three consecutive Canon items. I would be furious, especially at the poor service you've received.