Well, actually Primo is designed to work from SD, but who knows, maybe device is not. So try internal.
In that case, you don't even have to change the path, just rename the Primo folder to Navigon, and Primo.exe to navigon.exe. Of course, backup the original software

@Gjon
Which lang you tried? From package or some other? If other, first try this from package only. Delete device.nng.
Also, add this lines in sys :

[interface]
skin="ui_igo9"
vga=0
mapfontscale=100
show_exit=1

[rawdisplay]
class="landscape"
highres=0
screen_x=480
screen_y=272