Garmin released a new version of MapInstall a few days ago. Strangely though, I can't find ANY reference to it on their website, the only thing that comes up is the OLD version 2.1.6. (Remember, talking about Mac OS X here.)
I opened up MapInstall v.2.1.6 yesterday right before I was leaving on a trip, to double check that the topo maps on my 60CSx covered the area I was headed for. Something I do routinely before any trip.
Clicked on "install the update" to 4.0.0 and MapInstall opened up with NO indication of what maps are installed on the GPS. Crap. A blank slate.
Tried a couple WAG moves of quit-relaunch of MapInstall/on-off of the gps and nothing changed. (Also, a minor irritation that MapInstall now launches with the default view of the first map collection (alphabetically), rather than the previous version's last collection viewed.) The storage available bar graph at the bottom of the screen showed completely empty--4 G's available, despite the roughly 1 G of maps I'd previously installed on the gps's card. Double crap.
Thankfully I had a backup copy of v2.1.6. Deleted 4.0.0, copied 2.1.6 back in, and everything is back to normal.
My advice is to NOT install 4.0.0 until someone at Garmin can figure out how to correctly read the maps already installed via 2.1.6. As usual, stay away from any X.0.0 release.