Hi Beekeeper,
You didn’t have to purchase an upgrade to the program. If the install got hosed somehow and a repair didn’t work, the best way to fix it is to use the uninstall utility and instructions located on this page: http://www.avast.com/uninstall-utility
Give that a try (pay attention to the directions on that page!) and see what happens.
I also suggest downloading the version of Avast that you paid for to your desktop before the uninstall, so that you don’t have to go on the internet to download it when you don’t have any antivirus protection. http://www.avast.com/free-antivirus-download
Let us know…