Windows 8 + Online Armor + Firefox + Flash

Greetings!

I have two Windows 8 64-bit installations with Avast 8 free and Online Armor (OA) free and this problem:

Flash (e.g., http://www.speakeasy.net/speedtest) freezes Firefox unless Avast Behavior Shield (BS) has “Monitor the system for unauthorized modifications” unchecked or OA is shut down.

Of course, I would prefer to fully enable BS.

No combinations of exclusions in Avast (Global or BS or anything) and/or OA help.

Nothing is in the logs.

???

OA with its strong HIPS can monitor all the system for unauthorized modifications very well, so you might just leave that option disabled in Avast, in my opinion.