Thanks for all the ideas! I've looked further into these, the unsigned driver isn't an issue, it's just an old driver for an old sound card. As for the XBOX issue, I have removed some obsolete controller drivers I had installed for an XBOX 360 controller, and that error is gone.
Furthermore somewhere in my troubleshooting process I have cut total memory usage from ~95% to ~75% but this has not solved the problem. Next thing I am planning to do is to run a thorough memory test overnight, but I'm not sure if that will help, although by running further reports, it appears a lot of other games I own throw up a RADAR_PRE_LEAK_64 error. I've read that this is fairly common and nothing to worry about, but it still seems a little strange. Another idea I had was to update the BIOS, but I may hold off on that until there's nothing else I can think of.
In my mind a hardware fault seems most likely, since I cannot find anything that was updated or had a new version released in the time the game broke. Thanks again for all of the advice!
