I am not sure if the "NMEA input not valid" and the bad positions are related or not, but they could be. GPS systems output text data in a format specified by the NMEA. There are many different data sentences it can output and it's possible that some of them are not understood by Maemo Mapper (hence the error message). Alternatively, I think some (all?) NMEA sentences have checksums and/or give quality/validity information abotu the data they are providing. The error message can hence also indicate that the checksum failed or that the GPS marked some data as invalid. I find it highly unlikely that any checksums fail - usually NMEA is exchanged via 3-wire serial ports with no error correction whatsoever - hence the checksums. However, Bluetooth has its own checksum/retransmission protocol, so the data seen by any application should be completely error free. So it could possibly that the GPS is providing position data but is also marking it as invalid due to poor signal strength. That would also explain why the position is off in Maemo Mapper. I am guessing that is an intermittent thnig? You might want to talk to the Maemo Mapper author and/or file a bug report. It shouldn't make your position move by hundreds of miles if the GPS marked the data as invalid... Of course, it's also possible that the GPs doesn't catch all its error and that it sometimes provides bad data without marking it as invalid. Then it's just a limitation of the GPS receiver and you'll just have to live with occasional artifacts (although technically, Maemo Mapper could use heuristic checks to filter hundred miles jumps out...)

Martin