There was a typo in my post. I said "Instead gpsd" when I meant "Install gpsd". In order for the GPSD solution to work, you have to install gpsd (a package)
and start it up (from the command line) before starting Maemo Mapper (or at least before trying to connect). Does anyone have a good tutorial on how to use GPSD on the Nokia 770 or N800? If you don't know how to use GPSD, then you probably shouldn't try to use it with Maemo Mapper. Hopefully, a future version of Maemo Mapper will make it easier to manage GPSD, automatically instead of manually.