you said you tried some of the other things posted, could you tell us what?
Other common questions that we have to ask:
1)Did you have another A/V product before installing avast?
a)If yes, did you try that company's removal tool to fully remove the product before installing avast? (a list can be found here:
http://www.askvg.com/ultimate-collection-of-uninstallers-removal-tools-for-all-popular-anti-virus-software/)
b)If no, do you have a firewall that could be blocking avast's updater?
2)Did you try doing a repair install of avast?
a)If not, give it a shot
b)If you did, try a full removal by using the avast removal tool (found on this page w/ instructions
http://www.avast.com/uninstall-utility) after using the standard Add/Remove programs built-in to windows, then attempt to re-download and re-install avast again
What OS do you have?
