Here is a post from Wing-Rider on another forum:
They sent me a new one. Ver 4.60. While the problems mentioned above seem to be corrected, one thing still won't work. I can't put a newer map on it. It will only fully function with the supplied map which is 2011.10. I tried loading an unlocked map 2011.40 onto the nav and the map works fine but you can't do any searches by name. All the letters and numbers are shaded out on 2011.40 but not on the supplied map 2011.10. All the POI's are there because search for nearest picks all of them up. For some reason, it won't pick up search by name POI's. I also looked in an area that has many POI's, and I see them all. I wonder why search by name won't detect them but nearest will.
So, it looks like even with the 4.60 firmware, we won't have a fully functioning Navi if we use updated maps like 2012.40NT. Garmin really sux.