Maybe, after installing the SP1, you can reinstall avast from scratch:
1. Download the latest version of
avast! Uninstall Utility and save it.
2. Download the latest
avast! version and save it.
3. Uninstall avast from Control Panel (if possible). If, for any reason, you can't run it, try booting in
Safe Mode and doing it from there. Anyway, boot after that.
4. Run the avast! Uninstall Utility saved on 1. If, for any reason, you can't run it, try booting in
Safe Mode and doing it from there. Anyway, boot after you've run it.
5. Install avast! using the setup saved on 2. Boot.
6. Register your free copy or add the license key for Pro. Or even
upgrade your key from old versions.
7. Check and post the results. If, for any reason, you did not solve, try doing the step 3 in Safe Mode anyway.
Other option is to repair the installation through Control Panel.
Another one would be disable separate shields to see which one is blocking the connection (I bet on Web Shield or Behavior Shield).