I just installed basecamp, it looks quite different than Mapsource.
Did you already authorize the Plat map to use with this new GPS or an older one?
Did Basecamp recognize your GPS?
Do You have the Garmin communicator installed?
I just followed the instructions in the basecamp help section and it seems to be loading BLM maps just fine.
I do suggest following Hunting GPSMaps instruction for authorizing. I did and it worked for me. I think the garmin instructions are different and may create problems
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