Sebring, have you been able to resolve anything? I'm having the same problem with my Garmin GPS10. I've noticed that regardless of how the GPS is configured (as far as which NMEA sentences to transmit), after connecting with my 770 it only transmits the GGA and GSA sentences. I can reconfigure it with the Garmin software, connect/disconnect with my PC, and sentences will be normal. On first connect with the tablet, it will send some other sentences (because my GPS fix progress will increase), but then only send GGA and GSA again. It will continue to send only GGA and GSA sentences until I reconfigure it.

It is almost as if MM is sending some config data to the GPS, which I was under the impression that MM transmits nothing. Is there perhaps some way to verify that no information is being transmitted from the tablet to the GPS? I've seen some people discussing /dev/rfcomm0 for received sentences; is there an equivalent for transmissions?