Nope, Firefox 8.0.1 is meant to fix bugs on MAC then since it doesn't contain any improvement it wasn't distributed as update on Windows.
Anyway, I followed these steps:
1. rebooted Windows in safe mode
2. used the uninstaller tool to remove Avast
3. rebooted Windows and cleaned the registry
4. re-installed the latest version of Avast, re-registered it offline with the proper key
I confirm Script Shield still logs/scans with IE while it looks dead as a door knob with Firefox. The Real-Time Shields / Script Shield panel doesn't show anything being logged/scanned. I don't see any error, just while being on the same page with IE and Firefox, with IE stuff is logged/scanned while with Firefox nothing happens.
My OS is Windows XP Home Edition, version 2002, service pack 3, italian.
Information about Firefox and Avast same as above.