If you own a NVIDIA graphics card you should read the following bluepost from Datth:
"We're getting reports where users are getting intermittent low FPS after installing these drivers. It seems that it is related to the fan control included in these drivers not working correctly and is causing the video card to overheat on 3D applications. This will affect Warcraft 3, World of Warcraft and StarCraft 2 Beta. Please uninstall the drivers and revert back to the older ones."
As you can see, deleting the current drivers and switching to an older version is currently the best solution. If you seem to have familiar problems please report in this thread.