opencpn i setup to use port /dev/ttyUSB0 or gpsd
opencpn can also use gpsd, but if xgps cant use gpsd the neither can opencpn.
I did have some trouble at first figuring out gpsd config. I ended up doing a purge (complete removal
with configuration of gpsd and reinstall gpsd) then after doing the reconfigure command it worked.
also if you run dmesg after plugging in your gps device, dmesg will report the port assigned and other info. gpsd supports a lot of devices.
support for gps devices is programmed into the linux kernel
it sounds like gpsd is not working on your system. I am using ubuntu 11.04
It should be able to work for you