I ran into this issue and resolved it, just posting for the benefit of anyone else who makes the same mistake.
If you upgrade the firmware on your avic-Z# using the acronis disk image restore method and you have problems, make sure you have the 2010 version of acronis.
In my case, I happened to already have the 2012 version installed so I tried to use it instead. It wrote the disk image fine but the AVIC unit would go into a reboot loop trying and failing to apply the update. Once I downgraded acronis to 2010 and re-wrote the disk image, it worked fine.
Also be aware that there i
