Explosivegrass

I have recently started having a problem where when I move my mouse on ONLY ArmA OA, it lags to very low fps, making it impossible to click on buttons and makes the game completely unplayable. There is almost definitely no problem with hardware as I've been playing ArmA and Dayz for years and it's only been recently that the issue has started. I have changed my GPU_MaxFramesAhead and the similar options like mouse smoothing to zero. I am stumped on what to try next. Any help would be very grateful.