K, so let me make sure to be as descriptive as possible...
Like the threat title implies, Space Marine crashes in multiplayer. These crashes are completely random in terms of frequency and severity.
First, frequency. I've had stretches of entire days where there was no problem, playing for several hours each day. However, usually, the game will crash every other game or so, either in the middle or towards the end. Like, I can make it through one match, but if I follow that group and play another match, I'll crash. And sometimes, I'll crash, join again, and crash again. I mean really, I could join, crash, join again, play for a game or two, crash, rejoin, make it through my usual match and a half, crash, rinse, repeat. It's completely random.
...Can I just point out how frustrating it is when you're playing Seize Ground, and you're at 996/1000, and suddenly, the game crashes?
Anyway, severity. Usually I just crash back to desktop, get one of those ambiguous "If you report your error, we'll review it and get back to you" popups, and I close it and rejoin. But there have been times when I outright BSOD'd - that's "Blue Screen of Death" for those not familiar - and other times when I just randomly rebooted. There was a single instance where the entire PC just froze, and I had to manually hard boot.
So far I've tried shutting everything else down that requires bandwidth to conserve my own for Steam and multiplayer, and doing a Reinstall with the discs. The reinstall found no bad or corrupted files to repair, and the problems continued. Unfortunately, I can't determine if this is a hardware or connection problem. I mean I highly doubt that a person can lag so much that their entire machine suffers for it - pretty sure they'd just drop or disconnect first - but I seem to fare better on the smaller matches when it's just 4 vs 4 or so. Otherwise, honestly, I can't pinpoint any recurring variable, any one thing that contributes to the game's errors.
As far as what kind of rig I'm running, I can give specifics, but considering I overcompensated on everything simply to avoid these kinds of problems - I mean, I built this computer to be able to handle anything whatsoever I could conceivably throw at it - Space Marine is not at all the most system resource-intensive game I run on it, it barely takes up a fraction of my CPU or RAM. Also, Space Marine is the only game that I've had this kind of problems with, so frequently, in years.
However, to be fair, I'll also point out that I have a HDD I've been meaning to replace, as it's nearing the end of its operational lifespan, but considering just my OS uses it, and Steam and Space Marine are installed on a separate drive, I don't know if that could be the issue.
Anyway, if anyone has any insight, it'd be appreciated. I'll copy-paste this on the actual Space Marine forums and see if I can't get some help there as well.