Update on my situation. Sent the radio back, they sent me another one. Did the update before even finishing the install. This one works just fine. Nothing with USB would work on the previous one, so there was obviously a defect within the radio itself. So far so good with this one.
Trying to update the firmware on a new AVH-W4400NEX and having issues as well. I've tried USB and SD card with no luck either way. USB doesn't seem like it wants to work for anything. Can't get USB to recognize anything. Does anyone have any suggestions?? Should have bought the Kenwood I wanted instead of this crap!