Update your firmware with webupdater firstly
follow instructions the application gives you.
Then,i guess you have in your internal memory a preloaded old gmapprom.img.Code:Please Login or Register to see the links
Connect again your gps USB,backup it on your pc just in case, delete it from int. memory, copy in an sd (4 GB one should be enough) in a Garmin folder ,the new created gmapsupp.img.