If you are able to push routes to the GPS, then I don't think you have a driver problem.
What I find (with more than just the 350) is that after they have been connected to the PC for a while, they change state or something, and the PC doesn't see them anymore. I disconnect, then re-connect and it solves the problem. Refresh the mydashboard page a minute or two after doing that.
Eventual Master of the Obvious
2005 R1200GS | 2013 R1200GSW | SOHC4 208 | DoD 2032 | BMWMOA | BMWRA | YB