Turns out a similar solution that worked in Avast! 7 (found here
http://forum.avast.com/index.php?topic=98429.0) does in fact work in Avast! 8 with some minor adjustments. Here's what I did:
1. Open Avast
2. Press Alt+E to get to Settings
3. Press Down Arrow 20 times to get to Troubleshooting
4. Tab 6 times to "Enable Avast! Self-defence Module"
5. Turn off Jaws
6. Hit Space to check the checkbox to disable the Self-defence Module
7. Press Alt+O for OK
8. Wait 10 seconds, then Tab once and then Space. This is to confirm that you want to allow these changes.
9. Now re-enable Jaws and the screen should read. You may or may not need to close/reopen Avast!
To re-enable the self-defence module, follow the same steps but skip step 8.
Note: If you alt+Tab out of Avast at any point, you will likely have to close/reopen the interface to get it to read. Weird I know, but that works for me.
This was using Windows 7 64 bit, but I don't see why it wouldn't work on Win 8.
Hope this helps!