Actually,
On that note. lol.
We had this bunch of IBM R31's that developed very very very small cracks in their motherboards. This would cause them to freeze intermittently.
It took us a while to figure out what was going on with them though. We'd bring them in, run a full diagnostic on them, inspect all of the components and find nothing hardware wise wrong that we could detect... so we assumed it was a software issue, some new virus or worm that was going around. We kept formatting them and sending them on their way. Eventually the pattern became apparent, as they would keep coming back, and it was only the R31's.
Eventually, with one sitting there completely frozen despite everything I had done to it, I took it and gave it a good wack with my fist.... sure enough the unit started working again. We discovered that whenever it froze... if you hit it hard enough it would come out of it.
We mused for a while about just giving people rubber mallets to hit them with, but eventually decided to replace the defective boards instead...