Errrr.... the cat ate it?
In all seriousness... what happened. Is mouse pointer completely gone? Or is it just "locked" (stuck in place somewhere)?
The latter might be you having accidentally switched "mouse control" to flight by pressing a key/button (check you controller/keyboard map in that case for "mouse control toggle").
If its completely gone... maybe you have deleted the "cursor.bmp" in your AH2 folder somehow? Apart from that, if mouse is functioning properly in windows but not in game (even after relogging) im kind of at a loss...