Reading a few threads on the Gigablue support forum via google translate.
A fair few people are experiencing the same problem as me and Richard, some have had this problem since
January 2013 (not a misstype).
One person has two boxes, one runs perfectly fine, the other he has to put a fan under to get it to work perfectly.
Someone else had exactly the same problem, sent his receiver back, they replaced his motherboard, he now has zero problems.
Another has zero crashes with the lid removes, but the rebooting problem with it on.
Someone says in a post dated
February 2014, I also have a heat problem wit the box, when recording two programs at once and watching a 3rd. (them installing a fan solved all their problems) which makes me think it is a completely different issue from the recent driver problem?
Someone else says the heatsink is undersized for the CPU and then links to a long thread from January 2013 about adding a fan to the Quad. With many showing photos of their efforts, eg
View attachment 36908
So it looks like for most people there's no problem, but for a small but significant amount of people. overheating issues do occur.
But it's still odd that for many, it only happened after a particular update, a fair few posts appearing May this year. I still think it's simply a matter that some boxes run hotter for whatever reason, hence only a small number of owners get the problem with the newer software.
Most of these posts refereed to the actual CPU temp, not the reported 99C temp me and Richard have been going on about, but it was still the temp causing their issue. But as many of these precede the recent driver problems, I do think it's a completely different issue (although still very very very odd how it all started for me and Richard after the update).