Why did my fullscreen graphical performance decrease with Unity 3D?

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http://askubuntu.com – I updated to 11.10 and Urban Terror now seems very laggy in fullscreen mode when I'm using Unity 3D (Sync to VBlank is disabled). In Unity 2D I get good performance, but when I was using 11.04 I had great performance on Unity 3D as well. Why has this changed on 11.10? I like Unity 3D more and I don't want to log out and switch to 2D just to get good performance on games. My graphics card is an HD 4250 and I have the drivers installed. (HowTos)