Yes, One Eyed Jack, it works for me (Radeon 9600 Pro, DirectX 9.0c). The modified BlitzMax MouseX example below shows the lag - when I move my cursor around the screen, the white circle noticably lags while chasing it. By turning on your "magic," the circle remains glued to the cursor like it should. Nice workaround!
'Set to true to get rid of mouse lag in DirectX: Const OneEyedJackMagic = False Graphics 640,480 antiLag:TImage = CreateImage(2,2) While Not KeyHit(KEY_ESCAPE) Cls DrawOval MouseX()-10,MouseY()-10,20,20 Flip 0 If OneEyedJackMagic Then DrawImage antiLag,0,0 LockImage(antiLag) UnlockImage(antiLag) EndIf Wend