The other day I started up my GPS receiver, a Magellan Map 330, and it gave me an error about not having any maps installed. Grrr. Try as I might, I could not get a detail map to load, so I figured that something may have happened to the basemap. I found a file on my Mapsend Streets CD to fix the basemap, but it wouldn't do anything either.
Luckily, the Internet came to the rescue, with the most helpful site being the Map 330 Club Yahoo group. Long story short, I had to hold two buttons in (Esc and Nav) while pressing the power button, which puts it into Software Upload Mode. Then you can use a special Magellan utility to upload new firmware, and then upload the basemap. The firmware was actually an update of what I had installed, so I got a few extra features, which is cool. I wish the whole process would have been a little easier though.