I said I would report back to the thread I started, and so I want to do that now. I wish I had better news to report. I'm glad to hear, assuming it's accurate, that the problem was with a bad A/V definition rather than with the updated program, but for those of us who got in trouble, like myself, the consequences could still be unpleasant.
V.7 would not uninstall from add-remove, so rather than do the planned remove and reinstall, I decided the best way out was to do a system restore to prior to the time I upgraded, which was about a day earlier, and continue on normally with V.6 for awhile. System Restore worked, and I thought I was in the clear because both add-remove and the program said that V.6 was now installed. But the problems w/ V.7 got transferred to V.6, because V.6 now wouldn't update either, and it too was now uninstallable from add-remove. Since I already had the Avast uninstall executable for V.6 stored on my hard drive I tried to go into safe mode to run it, but in doing so made an operator error - totally my fault, but I don't do this very often so it is not a habit - and more or less borked my computer, which thereafter refused to get past the opening Thinkpad screen. Fortunately the computer repair shop managed to save the installation and I'm picking it up tomorrow. I'm posting this from a spare computer, without it I'd have been up the creek these past two days.
I really appreciate that Avast's business model includes a free version, so you won't find any vitriol emanating from here, but I have to tell you that this is going to be the most expensive free software I have ever used.
