Secondo quanto riportato qui:
[url]http://openmtbmap.org/it/download/[/URL]
il problema deriva dalle curve di livello se integrate in entrambe le mappe.
In pratica bisogna installare nel computer una sola mappa con le curve integrate, la open o la velo a scelta, oppure tutte e 2 le mappe senza curve di livello, con le curve di livello installate nel computer separatamente, in modo da inviare le curve di livello al gps una sola volta.
"Velomap and Openmtbmap of the same Country Problems
If you install an openmtbmap and a VeloMap of the same country with both times integrated contourlines, you should only send the contourlines once (meaning with either Openmtmbap or Velomap of the country).. Else you GPS might not show the maps, or worse not even start until maps are deleted. There are several possibilities.
a) Install both maps without contourlines and contourlines separately (install separate contourlines only map option in installer). You have not trouble.
b) Use the create_gmapsupp
.bat batchfiles and for one map select no contourlines.
c) be careful here: Select the map as usual in Basecamp/Mapsource or Qlandkarte GT, then go to the list of the selected tiles ready to be sent to the GPS, scroll down to the bottom, and unselect the contourlines only tiles from the list.
francesco