When I have my 60CSx plugged into my laptop via USB and select "mass USB storage" on the GPS menu, I hear the "ding" and temporarily see the device pop up on Windows Explorer but then it immediately disappears. What's wrong? :(
You need a microSD datacard in that unit to use USB Mass a Storage Mode. Only the microSD card mounts on your computer, but not the GPSr.
My guess is that you do not have a card in the GPSr. Can you confirm or deny this?