Nesivos. I forgot to thank you for your advice and like I said the firewall was not set up to let Avast! So I thank you because I predict this would of eventually become a problem.
You are welcome.
Is your version of Vista completely updated? Make sure that it is updated.
When you uninstalled Avast and then reinstalled it did you use the Avast uninstall utility?
http://www.avast.com/uninstall-utility
Also after running the uninstall did you clean your registry?
After using the Avast Uninstall Utility run at least one registry cleaner program using/including "Deep Scan"
Sorry I will not recommend any Registry cleaner programs because I don't want to be responsible if using the one I recommend messes up your registry.
You might also want to run a anti-rootkit program before rebooting.
After doing the above and before rebooting recheck the setting on your Windows firewall to see if there has been any change.
Reboot, using a "cold reboot" and again check your Windows firewall to see if the settings are different from before the reboot.
If everything looks okay you could then try and reinstall Avast.
What I am not sure about is if you can or should reinstall it in the "Windows Safe Mode". If you can you might want to consider that and then see what happens in the "Windows Safe Mode" I would however, double check this with someone who knows more about installing Avast.
Safe mode will not load all the Drivers on your system. There could be a Driver conflict in your system causing the problem but the conflict may go away loading Windows in the Safe Mode.
If the problem has gone away loading Windows in the Safe Mode then reboot normally and see if there is still no problem. If there isn't you are good to go. If the problem returns then you might have a Driver conflict. If that is the case I think you might have to compare what Drivers are loading in the Safe Mode and which ones are loading in the regular mode but not in the Safe Mode. You could then go from there, find the Driver conflict and eliminate.
The above is probably a long shot, but Driver conflicts have been known to cause all kinds of weird things to happen to the computers that the conflicts are on.
Just some thoughts. Good luck.