So, I've only gone ahead and made a forum account after exhausting literally all other advice I could find from Google searches or friends, but here goes. Every time I try to boot up Holdfast, it force-restarts my computer and my router. This doesn't happen with any other game in my Steam library. I have uninstalled and reinstalled it four times on two different HDDs, I've verified the installation every single time, and the problem persists. This has only started happening in the last 1-1.5 months. The only way I can get it to work occasionally is by unplugging my ethernet cable, booting the game, then plugging the cable back in. I really enjoy playing Holdfast with friends but at this rate, I cannot do so.
Intel i5-3570 (yes, I'm aware it's old but between being a grad student and it working acceptably for most other games it's pretty far down the priority list)