I have the same problem, recently Amazon send me the new firmware 3.1 (i have 3.0.3) and i stop the process (because i have a Jailbreaked K3 wifi and this day i didnt know what would happen).
Since this failed update i have my K3 with mac address unvailable, i cant connect to wifi and i cant upgrade manually the firmware (got U007 error). I cant uninstall the jailbreak. (same error, U007)
I tried hard reset my device and drain the battery but doesnt work
Help please!, What can i do?