After upgrading to firmware 4.0 i lost my ability to playback youtube videos or streaming videos, is there a way to downgrade back to 3.1? I have the firmware but when i insert the micro sd card in the unit nothing happens, all help is appreciated!

did you ever find a way to downgrade???

I downgraded my F90BT this morning, went from v4 to v3. The things I lost after upgrading to v4 came back as soon as I was back on v3!! So yes, it is possible.