Thanks to the sorry state of graphics drivers on Ubuntu, Flash–which is already terrible on Linux–can give you lots of headaches, including jerky video, slow scrubber movement, and not showing anything at all on the screen when you fullscreen video content found on sites like Youtube. The fix I found was as follows on my Ubuntu 11.04 64-bit system (although your configuration may not require every item in order to function properly):
- Run CCSM (compiz settings manager, get it from Software Center/Synaptic), go to OpenGL, and uncheck Sync to VBlank.
- Right click a Flash video, choose Settings, Display (the first tab), and uncheck Enable hardware acceleration. I had to do this through Firefox since Chrome didn’t want to let me click anything on or close the Flash settings box.