I updated my PC (Win7/64) this morning from latest 6 to 7.0.1426 and the computer started to run very very slow (to the point where mouse cursor only moved once every few seconds). I thought I'd better leave it, but after 2 hours the problem was still there, even after rebooting.
Went into Safe Mode, removed Avast (including using latest aswclear), rebooted and all was fine. So I tried installing again, and the computer was fine until I rebooted (it had said that autosandbox wouldn't work until rebooted), and the computer ground to a halt again.
This time I hit the hibernate button on the PC itself, the computer hibernated normally and, bizarely, when I brought it out of hibernation everything was fine.
Since then I've had phone calls from several friends (with XP or Win7) to say that they've updated to the latest Avast and their computers have crashed or frozen. I've been able to get one running smoothly again over the phone, but will have to visit the others to sort things out over the weekend.
So there is something clearly VERY wrong with this version and I think that we'll just strip Avast off and use something else.
It has certainly shattered my (our) faith in Avast