Although you are free to set it as you want, I want to be clear. I am NOT recommending to disable AutoSandBox. What I was saying is that you have the option to tell to AutoSandBox that a certain program (located in a certain folder) should be treated as “safe to run in normal mode”. That means leaving AutoSandBox enabled, but it won’t bother you with that specific program each time you run that specific program.

Yes. I found Avast update changing my theme/display/desktop/icons "unusual" too.

In fact, I’ve read before about problems related to display/desktop/icons and alike, but I have not read anyone saying that Avast (update) actually changed something like in your case.

I've also found a new issue. Avast is not auto-updating virus definitions like it did in the previous version. I realized I hadn't heard the little voice or seen the notification pop up, so I checked it. Had to manually update. Right now it's showing the last update attempt was: 9/13/2011 12:32:34 PM. But, the last update is the one I made at 5:33 a.m. I'm assuming this is a glitch, or it wouldn't be "attempting".
Have you rebooted after Avast update? Please do it again (and report back about the database update).