Disabling hardware acceleration works for me.Lucid 008,
About Nvidia, and GeForce card with a jerky video screen under Flash.,
I modified the screen resolution through 'xorgwizard' and put
1600 x 1200 x 24 (OK for monitor, maybe NOT OK for card) .
and now it's OK for me
seen on Adobe Forums :
"http://forums.adobe.com/message/972329#972329"
right clic > Flash settings > disable hardware acceleration > rerun the stream ( because options fields of Flash are completely grey !)