Have you read the release notes posted in the Uniden Twiki?You right and there is something different with the firmware but no details were released.
It clearly states:
Fixed an issue where starting of some vehicles caused the scanner's audio to stop working.
It appears that Uniden fixed the problem by forcing the scanner to reboot if the supply voltage drops below a set level. As others have stated, the supply voltage to your scanner may be dropping below the threshold allowed by the new firmware. As a result, your scanner is rebooting when you start the vehicle. How you solve the voltage drop problem is outside the scope of this thread.