to the OP: I could have swore i posted this up a few days ago, but anyway. There is a forum called
AVIC411.com there is a lot of helpful tips there.
I had an avic f900bt and I made my own themes and what not for it, it was a great headunit for me. Anyway, I had the same problem at one point while tweaking some things. It would reset over and over after the "initial boot"
What you need to do, to reset the firmware is to get it into what is called "test mode" you will need a sd card to do this. Just look on avic411 and look for testmode and how to install new/reset to original firmware. This should fix you up. It was a great forum that I used to be a part of for a long time. Hope this helps!