Are you going to load a map?
You can try to use WebUpdater. Run it with a command options like that:
WebUpdater /upload_file rgn=49 path=your_path\gmapprom.img -autorun usb /i
where "your_path" is path to your map in gmapprom.img file.
I found this info on the web, I don't have 278 so I can't check it myself.