I have suddenly got exactly the same problem as described by Vicki, which started earlier tonight. I am using AIS. I have tried doing a component update from "Programs and Functions in Win 7, but get an error message. I also tried downloading a current trial version of AIS and installed it over the original installation, but it hasn't had any effect. The Fix Now button has no effect.
The shields are all disabled and when trying to start them individually I get a "shield unreachable" message. I also get the end point message when trying to do a scan. The virus definitions are listed as "Unknown" they won't update as I am told that the Avast service isn't running, the program version is listed as 6.0.1367.
My registration/subscription details are blank, they've disappeared into the thin air, although the Subscription is listed as Active. When I try to insert the licence file I am told that no valid licence content was found. I still have more than a year left on a 3 PC 2 years Subscription !
Oddly the Avast Firewall is running fine, although it had been somehow been turned off when I first encountered the problem, but started without a problem. I also discovered that Win 7 Defender had been disabled too. Even more odd was that Windows didn't give me any warning that Win Def and Avast weren't running.
I had done a system restore tonight, but I don't think that Avast was running before that, as I didn't get the usual virus definition update tonight, so I have a sneeking feeling that Avast was disabled before I did the restore. I first noticed that it was disabled after the PC re-booted. I am no longer able to restore the system after the first install, I get a message each time telling me that my anitivirus program may be blocking it, and to disable it.. which of course it is. I have never had any conflicts with System Restore and Avast in the past.
I hope someone can help with this.