Mouse Control + Rendering Problems

This morning I decided to whip up a little terrain demo w/ mouse control. Everything went perfectly until I implemented the mouse control. I ran into a problem that I haven''t seen before. In both windowed and fullscreen, the scene does not render at all to the right of the place where the mouse pointer would be (whether the mouse pointer is visible or not). I know it has nothing to do with my rotation code because I can rotate with the arrow keys without the glitch. Is there something funky with the mouse that I am not aware of (I''m using windows messages for the mouse control, WM_MOUSEMOVE specifically). If I find no solution, I''ll go implement directinput mouse control instead... Thanks, Falkone