I don't think there's a fix for it. Every GPS system you buy should come with maps pre-installed. The maps will be on an SD card or on the device's own hard drive, if it has one. If the maps aren't there when you start up the device, return it to the store, it's defective. The maps are actually one of the more expensive parts of a GPS, but they are just software and could be corrupted.
i recently purchased a vrgp430wbc GPS system, and was pretty ticked when i found out that it doesn't come with any road maps installed, thankfully the one of the CDs that came with it will supposedly reinstall the road map, when i synced the GPS with my computer and tried to reinstall the maps it would get to the very end of the instillation process and then say there wasn't enough memory left for the map... now when i try and access the GPS function a 'fatal error' message pops up, i have sense bought a 1 gig SD card and tried the process over, still get the not enough memory message and i still cannot access the GPS function, does any one know how to fix this???

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic