The latest version of A-GPS has a new menu fuction "Info" which will tell you if nvd_data is valid or corrupted. My GPS had been working well but this AM failed. A-GPS told me it was corrupt when I ran it. Following maacruz's directions I deleted nav_data, powered down and pulled the battery. With an Internet connection I did get a GPS fix in a reasonable time. Just one note: nav_data won't be written until Maemo-Mapper is terminated. There may be a message here. nav_data may become corrupted if you exit MM without an active GPS fix -- purely a guess on my part. At least A-GPS can now tell us if nav_data is OK.