My other Shuttle box (SS51?, Celeron 1.3GHz) did die once, but that was a complete death -- and didn't appear to be thermal in nature (it was in a cooled 19" rack at the time). Having replaced the motherboard, it seems to be working fine now -- it's sitting here beside me running my website.
Oh, sorry, I'd thought that one was thermal (it was quite a warm cooled rack, as it were). Empeg's one had a PSU failure, and while again it can't be pinned conclusively on thermal problems, it always got pretty hot in there -- hotter than any of the PCs I've used except for the Pentium 233 desktop that used to overheat before I decanted it into a much bigger tower case.

Peter