This reply is an update to serveral previous posts, as well as, a response to recent observations and fixes.
MacBook Pro: 13” MBP (Early 2009) now running OS X 10.8.2 [also we have several other MBPs ... older and younger that do not exhibit the problem behaviour, ... All run OS X 10.8.2.] Each computer has an external mouse that is used about 90+% of the time. As others have said, when the problem occurs, the external mouse does not help.
Reviewing the posts, it could be that there are several root causes to the problems. Nonetheless, with very careful, frequent, and thorough cleaning, especially paying close attention to the edges of the trackpad that is slightly covered by the computer housing (as was suggested in a very early post to this discussion), the problem occurs much less frequently.
In my case, I suspect very small particles had become trapped between the TrackPad surface and the computer housing.
Others may have required battery or TrackPad changes ... but it is also possible that these changes dislodged or removed the particles, i.e., the hardware only needed to be cleaned thoroughly. Only the Apple folks could confirm whether there has been some sort of software change to the sensitivity of the TrackPad ...
So when the problem happens again, I:
- Clean the TrackPad and the edges of the TrackPad
- Reset the TrackPad by pressing evenly over the full surface of the TrackPad. ... as others on this discussion have indicated.
Cheers.