Steve,
There's definitely something screwy with Windows updates all of a sudden. I think that may be the issue as well. However, I don't see how they could really cause the problem with audio, then again, ya never know. I would think if Sonar is working and you have audio, closing Sonar shouldn't stop audio from working unless it's hanging in the background some how.
Also, I believe if you installed the hot fix you need to remove it before putting on X2a. Not sure how much of that matters really...but you definitely were visited by Gremlins.
Incidentally, Mike Mccue mentioned minimizing Sonar and running some other audio. I don't know about you or anyone else, but I cannot run ANY other audio applications when Sonar is open. I must kill the audio engine in order to have audio in other places. Just a heads up if you were to try his test and fail. That test wouldn't really be valid for all users....especially me. :)
Glad you got it fixed though. There are definitely a few Gremlins in X2 that I've never seen in X1 and below...so hey, anything is possible...but as long as you fixed it for now, that's all that matters. I hate when stuff like that happens. Especially when you have a well-oiled machine. I had a Windows update mess me up so bad, it sent my machine into a continuous loop and would not finish configuring. So they definitely mess things up from time to time. The latest ones seem to run one of my machines higher in RAM all of a sudden. I'm usually at 1.45 gig of RAM at idle before opening up a program. Now it's at 2.53 and it all happened after the last update. I don't put that box on the net other than for Windows updates. It makes me not even want to do them anymore I tell ya. :(
-Danny