Do you use a cloth pad? If so, try pressing directly downwards on the mouse without moving it across the mousepad. The idea is to move it along the Z-axis, but not the x or y-axis. You should notice the cursor moving diagonally. The Twin-Eye can track along the z-axis which can cause some weird tracking issues especially with cloth or other soft pads.
is there something wrong with a cloth pad? i tend to like them.