Recently I upgraded from Ubuntu Intrepid to Jaunty (9.04). Things are great, especially the boot time (my computer boots consistently in 15-20 secs since the upgrade). But somehow since the upgrade flash videos on websites like youtube, hulu etc have had problems with fullscreen view. The video becomes seriously choppy when seen in full screen mode and the usual reinstall of flash plugins didn't seem to make it any better. This was quite annoying especially since this issue didn't exist in Intrepid (8.10) or previous versions of Ubuntu.
After a bit of web search, I finally stumbled on the right solution. The solution, as usual, was on Ubuntu forms in this post and in bugs.launchpad.net here. In short, do "lspci -vv" and find the VGA output. Then find the right address to be added in the file /proc/mtrr. Apparently, the write-combining method of accessing the MTRRs has been affected due to a missing line in /proc/mtrr file. Adding the right range for write-combining lets the graphics card work much better.
I followed this method. Find the 'prefetchable' memory range and substitute in the 'echo' statement to the file /proc/mtrr.
And enjoy watching the daily show in full screen again!