My card is also affected and adding "EnableLinuxHWVideoDecode = 1" to /etc/adobe/mms.cfg (and restart Firefox) helps for my setup without any obvious bugs/artefacts added.
# lspci -nn 01:00.0 VGA compatible controller [0300]: nVidia Corporation G92 [GeForce 9800 GTX] [10de:0612] (rev a2)
My card is also affected and adding "EnableLinuxHWV ideoDecode = 1" to /etc/adobe/mms.cfg (and restart Firefox) helps for my setup without any obvious bugs/artefacts added.
# lspci -nn
01:00.0 VGA compatible controller [0300]: nVidia Corporation G92 [GeForce 9800 GTX] [10de:0612] (rev a2)