Thanks. There's the possibility that the two USB-serial adaptors are competing for the same port or otherwise colliding... could be driver-related.
There might be a way in the driver or system config to force the USB adaptor COM ports to a higher number. I think my USB-serial adaptor shows up on COM6.
Enlighten us - why do you need two NMEA ports on the netbook? Can you not just take a single
NMEA output from after the hub, which should take care of merging the GPS
As a general principle, I aim to have the fewest possible connections running to a laptop
. (0 - wireless is ideal