http://alpineclub.org.nz/news/2012/garmin-gps-update-warning

Anyone who owns a Garmin GPS and intends to continue to use it
with 3rd Party Maps must not upgrade their firmware.

Garmin have recently released a firmware update for many of their GPS products.
After updating a 60CSX to V4.00 we have been advised that a big change that
Garmin do not warn you of - all 3rd party maps (such as FreshMaps and
Memory-Maps) are BLOCKED so you will find that your maps can no longer be viewed
on your map capable GPS. Garmin will now only support their maps - which they
sell for US $220.

http://www8.garmin.com/support/download.jsp