there is probally a hidden partition or folder that it looks for that is not on the 'backup'

I ended up returning the 4100/U260 and got the 8100.... happier camper since.  After all, the price was the same...  

What do you like better about the 8100 versus the 4100/u260?  I am trying to decided on the 8100, 7100 or 4100/u260 combo.

Well the screen is much better (duh), the Navi seems to have better definition a far as what you're looking at.  I know the 8100 (not sure about 7100) has the 3D buildings, of which is not a huge deal, but kinda neat sometimes...

My gripe with the U260 was that because it's seperate it was telling me that I needed to insert the SD card a few times... (that is what it uses to store the maps)

I went the 8100 route because the difference in price from the7100 to the 8100 wasn't very much...$75 at the time..

the 7100 is basicly the 4100 with the U260 built in (and hopfully as good of maps as the 8100)

it probably doens't help much, but that is what I remember...  

Thanks! I want to be able to run the built in Navi and CarPlay at the same time, which I understand you cannot do with the 4100/u260.  In reading some reviews posted Amazon, some reported that dust gets in between two layers of the screen on the 8100.  Having never seen an 8100 I am unsure about this.  Does this seem possible?

I can sort of see where that could happen... I got a screen protector and hopfull it'll help there...

THe only thing that takes over everything is AppRadio, I havn't been able to play my iPod or HD radio when that is going....  I really don't plan to use it much if at all...

Just got mine installed. I tried to make a back up using a different as card but all I get it can't use maps due to license error

did you ever figure out a fix or workaround? im dealing with same thing