Playing player versus CPU...restarts my computer?

I bought this series on preorder through Steam, and I’ve enjoyed it immensely. Right now, however, I’m not, and for the simple reason of not being able to play any player-versus-CPU games when I’m not doing the campaign. This has only started happening within the last week; I saw there was a hotfix or something during this period.

Now I admit, I don’t have a great computer for this (I have an HP Pavilion p7-1012, an antiquated PC with an antiquated, integrated graphics card - so yeah, it’s old, and I can’t get a new one), but up to last week, this computer ran the games fine; I was able to play through the campaign for HW1 with a minimum of fuss. Now, however, whenever I start a player versus CPU game, it doesn’t just crash - it completely restarts my computer. Either it freezes up the moment my mothership enters the map, or a moment or two later, while I’m trying to start building things.

The only mods I have added are a small map pack from the Steam Workshop, so I don’t think that is the cause, but…I’m at a loss here. This was not happening for the first week or two since the release, and now it is.

This looks like a lot with a hardware problem, more likely with overheating.

Maybe; I run everything on low settings, though, and as I said, it worked just fine before; it only started doing this when it applied an update (which was towards the beginning of the week, as I recall).