I've tried three different Wheel Mouse Optical 1.1a now and with every single one it's impossible for me to draw a straight line in Paint/PS/Paint.net. The cursor breaks out top and bottom.

I suppose this isn't the norm? I thought someone was selling me some cheap WMO 1.1a knockoffs or something, until I tried it again with a friends original boxed wmo 1.1a and the same problem occurred.

I also tried it on a XP sp3 machine, same results