I've had the same problem with the V6 beta and my SP3 - loaded all the required maps onto the data card, done a route well within the loaded maps on the PC and loaded it onto the SP3.
When I tried to use the route the SP3 says "The route has an unknown format. It will not follow the roads precisely. Do you want to recalculate? Yes recalculate, No, use it anyway. I've informed Garmin.