I can't understand why this would happen it is usually a case of it eitere works or it doesn't and it is usually the firewall that is blocking ashWebSv.exe.
Have you tried it with a different browser ?
Does this happen with all web pages or just a limited number ?
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. You need to be on-line to do this.
If that doesn't work try, uninstall, reboot, install, reboot.
It would probably be best to download the latest version of avast and save it to your HDD, somewhere you can find it again. Use that when you reinstall.