This isn't a big deal but it is really irking me. My new Intellimouse Optical 3.0 doesn't seem to sit flat on my desk. It will rock ever-so-slightly from side to side (if my hand is over it and I put more weight on one side it will become uneven). Do all Intellimouse Optical mice do this? Is it some sort of defect, I'd like to go exchange it if so.