flash player lag on fullscreen

Hi,

when i play a video in youtube on fullscreen it start to slow down. I have Nvidia Geforce FX 5500, latest version of flash player and a don't have hardware acceleration on ! Is there a solution ? Nvidia does not support my video card anymore so i have the posably latest drivers, but i think they are quite old...

Thank you !

P.S. Sorry my English is not so good