I followed these steps that I found here:

[i]At this time, I suggest you a ‘clean installation of avast’:

  1. Download the avast! setup (current version 4.1.319). Take note of your Registration key or, if you need another key, the registration form can be found here
  2. Desinstall avast (Control Panel)
  3. Boot
  4. Use Avast Uninstall for complete desinstallation
  5. Boot
  6. Install the downloaded setup file
  7. Boot
  8. Enter the Registration key and configure avast! for your needs [/i]

As soon as I enter the reg key provided via email, I get the same error box.

I deleted and re-downloaded several times.

No other anti virus, but I am using Zone Alarm and have always used it with avast before.

I can’t think of anything else!