I had the same problem for months. i don't know what part of this worked or if it was a fluke that it finally worked. I downloaded the newer firmware for the garmin and installed it ( http://www8.garmin.com/products/webupdater/
) then tried adding maps, that didn't work, then tried 3-4 times resetting the garmin, and each time tried adding maps and it didn't work - turns out I wasn't really resetting it (I think) it appeared that the successful reset was holding down the clicker key and the pages key while starting up, and keeping them held down for a long time (15 seconds?) - there was no sign that it was resetting except a faint illumination, then when I let go of those 2 keys it went through the setup sequence. the only way I knew it had finally reset was when the page came my pointer was in the middle of the united states. I had repeatedly tried resetting before and the pointer/map page came up to where I was last at, so it hadn't really been resetting. I'm very displeased that it took 5-10 tries to get this to work and this happened on 2 units.
I reloaded the maps after it had properly reset and they actually display and are on the map list!
this is the second etrex unit ive had this problem with, and the first one was just as flaky - taking many reset events (see master and super master reset on other etrex threads at this site)