First do a program update through right-clicking the ball in the tray (it is now v. 4.8.1229)
<snip>
If you check the original post, GUITARMANONTHE is trying the manual update and it is failing, so can't update through the normal channels.
@ GUITARMANONTHE
Try a repair of avast. Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.
If that doesn't work try, uninstall, reboot, install, reboot.
It would probably be best to first downloading the latest version of avast from the web site,
http://www.avast.com/eng/download-avast-home.html and save it to your HDD, somewhere you can find it again. Use that when you reinstall.
Important before going through this to confirm that your registration is in date, right click the avast 'a' icon, select about avast, check the Updates expiration: date if that is out of date you will need to re-register as has been suggested.