Yeah, I got tripped up on this the first time I saw the unauthenticated status.

Something to point out that might be of importance. Ballebar in [Only registered and activated users can see links. ] states "The GPS might still need the GMA file for that unique unit if the GMA technology is implemented in the newer firmwares." He then mentions using an unlocker to fix the problem, which in fact is the right solution. However, the sentence I quote from him here is inaccurate.

ALL Garmin nuvis, regardless of age, will encounter GMA authentication problems if the maps are not unlocked. My 200W hasn't had an updated firmware released in over three years now and is an earlier unit in the run (n2 S V4 1GB SIRF). It refused to use the new maps unless I unlocked them with Fast IMG Unlocker.

GMA authentication is solely within the maps and has absolutely nothing to do with the firmware.