It seems to me you don't have enough power to start the video card anymore. If your power supply was close to the minimum required and/or you use adapters for the 6-pin and 8-pin PCI-Express connectors, the power supply may be inadequate. Running the power supply at maximum output for extended periods of time can shorten its life. I don't see any reason to update the BIOS in order to run a HD 3850x2.
HD 3850x2
Power Requirements:
Minimum 550 watt power supply both a 6-pin and 8-pin PCI-Express connection