My mouse pointer changes when I roll the wheel.?

I've got Windows 7 Ultimate. My mouse pointer is normally aero_arrow, but when I roll the wheel, it becomes erm.. well, i can't find it in C:\Windows\Cursors so I don't know what it's called, but it shouldn't change, right? I even changed the mouse properties, and it reverts whenever I do, but it still changes back to THAT pointer when I roll the mouse wheel. How do I fix this?