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[Bad Sector]

On my comp (diamond) I have to play with vsync and re-check the vsync after alt-tabbing or the MMB-camera sens goes down by like 300%.

I had this issue in another PC, though it doesn't seem to happen on my current one (might be AMD's crappy OpenGL implementation not being able to go above 100 fps in game :-P). If you do not like the extra input lag vsync adds, try using RTSS instead and limit the refresh rate to 60fps or so (might sound weird if your monitor is at 60Hz already, but framerate limiting will both prevent extra frames to be queued -though your drivers might have an option for that too- and most importantly, with vsync the reaction to your input will always be delayed to the next full monitor refresh whereas with frame limiting you'll see a partial update before the current refresh ends).