I have a new 2460 and when I did my first map update, I clicked on options or something other than "next or continue" and it offered me 3 choices, GPS, GPS and Computer, Computer only. I selected GPS and Computer. I already had MapSource from an old StreetPilot 2610. If you don't have MapSource, go to the Garmin Training Center and download it first. I did the same on my notebook and only selected "Computer" but the GPS has to be hooked up so the map will be unlocked.
It all merged perfect, but took about 3 hours. I have been able to upload routes and waypoints from my computer to the 2460 but it limited me to 3 routes. After that, if you try to upload a 4th, when you go to trip planner, you get the "hourglass" that never goes away.
I am going to buy a microSD card to see if I can upload to it and the GPS will work with more than 3 routes.
Anyone with other ideas, please let me know.
I am spoiled since I have done everything on my computer since 2003 using MapSource and have about 150 routes saved and I would load 10-15 to my 2610 each time I was gong to be in a certain area.