rhythmbox doesn't see mounted music player

[Rob Owens <rowens@ptd.net>]

I've got two different Sansa Clip+ music players, both set to MSC mode.
On my main desktop machine, Rhythmbox will these players once they are
mounted.  On my laptop, neither player is seen, even though they are
mounted.  Both computers run Squeeze.  Both computers have the same
relevant file in /usr/share/media-player-info.  Both computers have the
same plugins enabled in Rhythmbox.

Any idea what I should look for?  Maybe some configuration settings?
Maybe a package that's not installed on the laptop?

-Rob