Matrox G550 low profile PCI

Hi all!
I need to enable 4 monitor layout!
I'm using a motherboard with intel i830,
and a Matrox G550 with double cable.

I'm able to see Intel VGA, Intel TVOUT, Matrox first VGA and Matrox
second VGA.
But on the Matrox output I can see only flickering images ... all is
unreadable!
I've tried a lot of resolutions or bpp modes... but no changes!
Have you ideas????

Thanks!