I have a related problem.
I updated a few weeks ago but had no problems at first. Then windows threw up a warning that I was not protected.
The avast icon had disappeared from the start-up screed and I could find nothing on the computer about it- but my computer skills are only basic. However, I still got the flag showing regular updates.
I downloaded avast again from the web.
I no longer get the warning from windows but the red cross / yellow icon tells me that I am not protected.
When I open avast 'Current Status' it tells me the real-time shield is off and the Mail shield is off.
Both of these have 'Turn on' buttons which have dots in their centres.
I have tried all permutations of clicking the 'Fix Now' button, clicking the 'turn on' buttons and restarting each time. Any advice will be gratefully received. Col
Did you have any virusprogram before installing avast ?
Have you removed it using ad/remove programs and reboot ?
Have you then run the uninstall tool for that program to remove all leftovers and reboot ?
uninstall tools can be found here
http://uninstallers.blogspot.com/have you tried avast repair ?
For a repair of avast. Windows, Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.