The GPS driver writes a almanac /var/lib/gps/nvd_data which it uses in subsequent times when the driver is started. Almanac contains orbit information on all satellites, clock corrections, and atmospheric delay parameters. It is transmitted by a GPS satellite to a GPS receiver, where it facilitates rapid satellite vehicle acquisition within GPS receivers. It appears that if the N810 is powered down during this write the almanac will be corrupted. As a result it is recommended that after terminating Maemo Mapper during a session with a successful lock you save an almanac copy for backup purposes. Open a terminal window and run:
cp /var/lib/gps/nvd_data /var/lib/gps/nvd_data.bak