Just so that nobody else goes through the pain I did, I thought I would post this. Tonight I went back to REI and hooked up the etrex fom their display case in the store (version 3.30) to my D200/MC35/Serial setup and it worked fine. I then hooked up the new one they sold me last friday (version 3.51).

The newer etrex did not light up the GPS symbol, and would not imprint data onto the photos.

I swapped the new one for the one in the display case, so personally, I am all set. But this seems to be dire news for those who come after me.

Before the etrex I also bought a geko 201 which came with software version 3.70, and it doesn't work either despite the widespread use of gekos elsewhere such as red-hen and many DIYS setups seen on this forum.

Other threads have speculated that this is due to an (alleged) power-saving enhancement that causes the gps unit to not send signal until it receives power/signal on the input line... If this is true, the problem may be present for a wide range of new Garmin units. I emailed Garmin tech support but haven't heard back.