I THINK I got it all sorted out.
What I ended up doing was uninstalling the latest drivers
, which include Realtek's HD Audio Manager. Then in device manager, I scanned for new hardware and it installed my sound card as simply "High Definition Audio Device", and I just put the PC to sleep, woke it up and still had sound.
I can only assume their latest driver
and/or audio manager is just terrible and was somehow causing the problem. And seeing as how my sound works just great without that driver, I'll just leave things this way and see how it works out.