Updating to V7.0.1407 caused so many problems that I had to completely uninstall it and revert to V6.0.1203. I have XP SP3 with all updates and only use its Administrator account for installations and maintenance; all other activities are conducted on a separate Limited account. After updating Avast, Windows applications in the Limited account that connect to the Internet like browsers and a mail client would either not run at all or would not connect (Firefox would not come up at all, while others would come up but would not connect). Even some basic Windows elements like "My Computer" would only display a blank box with no listings; furthermore, those apps and elements that did come up could not be shut down (program "is not responding", and "quit now" would not work, also quit attempts via the Task Manager), nor could the computer be shut down via the RUN button - it was necessary to do a hard (power off) shutdown.
After restart, following the instructions given here by avast! team, I used the "avast! Uninstall Utility" to completely remove V7.0.1407 plus folders, and then rebooted to the Administrator account to do a clean reinstall from scratch. Upon completion, applications seemed to work while I remained in the Administrator account, but, as was the case earlier, they still would not work when I switched to the Limited account,
and again, programs there and the computer itself could not be shut down via the RUN button.
So, once again I used the "avast! Uninstall Utility" to completely remove V7.0.1407, rebooted, and re-installed the previous V6.0.1203, which works normally in both the Administrator and Limited accounts. Unless someone can suggest other steps to try, I will not be able to use V7 in its present incarnation.
I suggest an installation from scratch:
1. Download the latest version of avast! Uninstall Utility and save it.
2. Download the latest avast! version and save it.
3. Uninstall avast from Control Panel (if possible). If, for any reason, you can't run it, try booting in Safe Mode and doing it from there. Anyway, boot after that.
4. Run the avast! Uninstall Utility saved on 1 in Safe Mode. Boot after you've run it. Repeat this for any major avast! version you have ever installed/upgraded in your computer.
5. Install avast! using the setup saved on 2. Boot.
6. Register your free copy or add the license key for Pro. Or even upgrade your key from old versions.
7. Check and post the results. If, for any reason, you did not solve, try doing the step 3 in Safe Mode anyway.