When I upgraded from Linux Mint version 6 "Felicia" which is based on Ubuntu 8.10 to version 7 "Gloria" based on Ubuntu 9.04 my video performance started suffering badly. Worst of all, I couldn't watch videos using any of the applications installed vlc, miro, gmplayer, mythTV, Totem.
To see the kind of errors I was getting refer to my bug report
What worked for me was reverting the Jaunty Xorg intel driver to 2.4 as explained in this link
Then I edited
xorg.conf adding the following to the "Device" section
Option "MigrationHeuristic" "greedy"
Option "AccelMethod" "xaa"
I don't know if changing
gstreamer-properties Default output to "X Windows System (No Xv)" had any effect but it is working so I also left it.
Just in case you are wondering. Here is the result of "lspci -nn | grep VGA"
00:02.0 VGA compatible controller : Intel Corporation 82865G Integrated Graphics Controller [8086:2572] (rev 02)
So this solved it for me. I am no longer getting the error in Xorg.0.log and my video performance is better than before. MythTV, vlc and gmplayer work at full screen using a fraction of the CPU. Still some choppy video with Miro, and Totem is not displaying video but I am not getting the error.
If I have some time I will try moving up to 2.8 as explained here: