I have a 2u Server case, and my dual CPU fans are too tall - they bump up against the case when the top is put on, and the Server eventually freezes. It runs fine without the cover, and I'm quite sure the heat has nowhere to go with the cover on.
I've been to local shops to try to find a combo heat sink and fan which is lover than the current 2.5 inches which is not working. It's a socket 462 (I think), if that makes a difference. Any ideas?