Mouse lag in > 200fps weirdness

I recall seeing this before in other games and for the life of me I cant remember the casue/fix.

Basically, sometimes when I run air ace at the main menu (where we render a bunch of full screen alpha effects) I get a pretty nasty > .5 sec mouse lag.

That is, I can move my physical mouse.. and about half a second later, it appears on the screen.

I do recall reading about this exact issue, but simply dont remember what fixed it.

Anyone else had this or remember what causes it or what fixes it?

Phil.