Problems with Sapphire X1950GT and Abit motherboard

Hi, i recently installed a Sapphire X1950 GT, PCI-E, 256 Mb on an Abit
AB9Pro / Core 2 Duo E6600, 2 Gb RAM (bios rev. 17).

Everything was working fine till i upgraded the bios of my graphic
card to solve fan problem as stated on Sapphire web site. Now system
doesn't boot anymore, ABit hangs on 9.0 post code (Abit says that this
code means mobo is ready to start bios... but something doesn't let
bios to start... maybe ATI card?).

I checked my system with another video card (ATI x550) and everything
is fine, i checked Sapphire X1950 on another system (another core 2
duo E6400) and on this system vga card works fine... seems that
something between vga bios -004 and Abit is incompatible.

There's a way to revert x1950 to older bios? Unfortunately i can't
find it anywhere.

Thanks in advance
Luca