Have you tried using gigabyte's vga@bios to flash the card?
I had a problem installing it and getting it to work, but a reboot had it install and backup then flash my card bios without issue in about 10 seconds.
I have one of the 5870 coolers, but made a mistake on my 5870 purchase itself (I bought it after I ordered the cooler and got a gigabyte UD card, not knowing that non-reference cards were already out), so I haven't installed it.
I don't really have much to say about it outside of the card...