Direct Input using buffered data

Is anyone out there using direct input using the DirectInput8 buffers? I''m using them in my application and the mouse movement is jittery. For some reason, the Y axis doesn''t react as freely as the X axis does during movement causing the mouse to feel like your moving it diagonally at the top of the screen. If anyone has smooth mouse movement working using DirectInput buffers I''d appreciate help in making it work for my application. All of the FOREGROUND/EXCLUSIVE modes did little to help, though I am now using FOREGROUND|EXCLUSIVE instead of BACKGROUND|NONEXCLUSIVE. Thanks Kressilac