Same thing happened to me - I had to restore my computer, and now Avast won't run. I tried going to add/remove to repair it, but it won't let me do anything to the program because it "cannot read the program data from [filepath]". I tried uninstalling it so I could reinstall, but it won't let me do that either. Short of manually deleting all the avast files from my program files, I'm not sure what to do. To cover my bases, I have already rebooted a few times, tried downloading and installing a new version in hopes that it would uninstall the old one (no luck), and tried to re-start the program from within the user interface. Suggestions?