I suggest that you try a clean reinstall:
- Download the latest version of avast (AIS) 6.0.1289,
http://files.avast.com/iavs5x/setup_ais.exe and save it to your HDD, somewhere you can find it again (if you didn't save your last download). Use that when you reinstall.
- Download the avast! Uninstall Utility, aswClear.exe
find it here and save it to your HDD (it has uninstall tools for both 5.x and 6.0.x).
- 1. Now uninstall avast! (using add remove programs, if you can't do that start from the next step), reboot.
- 2. run the avast! Uninstall Utility from safe mode, first for 5.x if previously installed and then for 6.0, once complete reboot into normal mode.
- 3. install the latest version, reboot.
What firewall were you using when you only had avast free as it didn't have a firewall ?