Did you unlock the maps properly? I would use mapsource to generate maps. You can actually replace the build-in map with the webupdater program that comes with Garmin.
This is the command line instruction:
C:\GARMIN\WebUpdater\WebUpdater.exe /upload_file rgn=49 path=C:\Garmin\GMAPPROM.img -autorun usb /i
Rename the map generated with mapsource to Gmapprom.img (for this example it must be located in C:\Garmin)
This works for the C340 and C330. The C330 only has 1Gb internal memory (2Gb for the C340), too little to fit the latest complete European or N.American maps. You will have to select a subset in mapinstall and create a seperate map for the remainder and put that on the SD card.