I copied my fix for the USB not reading from the "z" forum where I had originally posted it. It may be a software driver issue that causes this to occur but this fix worked for me:
"I thought I could add a troubleshooting step for anyone that believes they may have bricked there RA3 or RA4 radio while trying to update the firmware. When performing the firmware upgrade on mine last week everything went as expected until I selected "Yes" to update the firmware and the radio rebooted. From this point on the radio would only display "Please insert update USB". I never removed the usb flash drive with the ISO image on it and could not figure out why it would no longer read the drive. After trying multiple flash drives I realized that the radio was not powering the center console media reader after it restarted to perform the update. I attempted to use a powered hard drive to continue the update but that did now work either.
Initially I had given up and had spoken with LKQ who was going to refund my money. In a last ditch effort, I resorted to trying to use the grey USB plug on the back of the radio with the following adapter I purchased from amazon to rule out the media reader itself as the problem:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
I plugged the above adapter directly into the radio on the back where the grey factory plug goes and then plugged the USB drive directly into the adapter. The radio began updating immediately after the flash drive was plugged in and now is much more responsive then before with the old firmware.
So for any of you that think you may have bricked your radio, give this a try before chalking it up to a loss."