i turned v-sync to always off and can't find anything that look like a "pre render" or "render frame ahead of time"
I still have that problem..
BUT
in fullscreen mode, without frame limit i have no mouse lag! (but i can't play on FS 'cause i have a widescreen monitor) Game runs at 1400 fps :\
in fullscreen mode, with frame limit i have mouse lag and game stutters..
in windowed mode, with aero i have mouse lag (with or without frame limit)
in windowed mode, without aero mouse lag is almost absent (with or without frame limit)
So.. i suppose the problem is in ATI driver :\ Can't be a problem of videocard performance, with this HD4850 i can play crysis at 1650x1080 with very high level detail :\
ah, i tryed OpenGL mode too
With opengl i don't have mouse lag with aero On (or i can't fell it) but frame limit don't work, i'm always over 600fps.
For the moment i play in OpenGL mode