Trust me, copelander, a mighty mouse that will not scroll in one direction is almost always simply dirty. I have two (one BT one wired) each of which I bought very soon after they first came out. Essentially failure to scroll in one direction means that one of the four directional sensors that it relies on has got clogged.
Cheby (above) describes the usual solution very well. Simply disconnect the mouse, hold it upside down, and rub the ball vigorously in all directions on a clean piece of paper. Try to avoid "running over" any of the tiny black specs that will probably appear on the paper , as the ball is good at picking them up again.
If things have progressed beyond the this, the tip of something like the plastic toothpick that comes with swiss army knives, or a cable tie, worked gently in around the edge of the ball, can help, but be gentle so you don't damage the mechanism. Some people also use a dab of isopropyl alcohol on a clean cloth applied to the ball.
To keep your MM running smoothly for a long period, clean it using the "rubbing on paper" trick AS SOON AS you get the slightest sign of bad scrolling, or every few days, whichever comes sooner. Once you have done this for a while you will find that the problem becomes much less frequent, as the internals get rid of any accumalated residual gunk.
People who smoke, and those whose hands get oily or grubby for one reason or another, seem to have more problems with this issue, and might want to think about a regular 'wheel" mouse instead, but I've found that a minute of preventative maintenance every few days keeps my MM's scrolling beautifully in all directions. I haven't noticed any difference in the behaviour of the wireless or wired models in this respect. They both use the same scroll ball mechanism, so this isn't surprising.
As far as choosing between a wired and a wireless one goes for use with an MBP the wired one is lighter, and probably uses less battery than having bluetooth running all the time. On the other hand, the BT one can be handy if you are working in cramped quarters, and don't want a jumble of wire to deal with.
Cheers
Rod
Message was edited by: Rod Hagen
