From your fix, it sounds like there's a design fault with the block and it doesn't surprise me. It looks like there should either be more clearance or an insulating pad covering in a few places.
I had a three-fan, three-slot Arctic Cooling cooler for my HD 2900 XT (yes, it was ages ago) that bent the card when the screws were tightened. I tried two samples of this cooler and they were both the same, so it was a design fault.
While the cooling performance and noise were great, I ended up getting a refund on them and going back to the stock cooler. I upgraded that card a while later anyway, so the whole thing was moot.
Siggie in the post.