He has a Tour which has a known issue with the trackballs. You can bump up the sensitivity to 80 and it help a bit. You should take it back and have it replaced.
if it's new, take it back. If not, you may have some junk in there. You can try to air it out, but most likely you had better have a service person look at it.
I wouldn't recommend taking it out yourself unless you do it for a living...those babies aren't like a computer mouse and are 1/10th the size.