Originally Posted by Crab Sandwich
After all the work you've put in to fix this already, I feel almost bad coming in and telling you that your problem is most likely going to take three clicks to fix!
The Xonar line of audio cards, which you mentioned you have, has a known incompatibility with bethesda's game engines (the worst being Oblivion, where it crashes immediately upon moving). The cause is Xonar's "GX" mode, which is basically a simulated EAX. This mode is on by default, and turning it off will most likely fix your problem.
To turn it off:
1. Double click on the Xonar Audio Center in your task bar.
2. Click on the "GX" button so that it is now off.
3. Close, and hopefully enjoy Oblivion and better stability in almost all your games.
I hope this works for you!
WOW. Thank you. That's exactly my problem, I will try that once I get home.