Dang! The same thing just happened on my GPSMAP62ST. I upgraded the unit and now nothing will show on the map page that I've created such as waypoints or uploaded to the unit ie geocaches. The caches are on the unit, I can navigate to the geocache files while the unit is connected to my computer, I just can't get them to show up on the geocache page or on the map page...kind of a shock while deciding to go treasure hunting today.
On a lark I attempted to upload a GC that is already on the unit and I got the overwrite warning saying the GC already existed, so I know the GC's haven't been deleted, I just can't get the unit to recognize them.
Thanks for any help with this, I'm crushed my unit's out of commission for the time being.