all you need to do is reset bios on the motherboard. i had the same problem Gigabyte GA-MA78GM-S2H and 9950.
you can use a flat screw driver a cross the pins and make sure your power is disconnected. this should work and it will run very hot untill you
download drivers ect.
Here's a similar story: GA-MA78GM-S2H (rev 1.1) would not boot except when after performing a bios reset, doing this you can get to the bios setup screen, from where you can press F8 to do a bios update, I downloaded the latest bios (using my laptop):
stick that on a USB drive (which must be formated with FAT) and after that it has been a happy computer. To reiterate the bios can update itself without booting an OS, which is very nice of it, I think.
Wish I had known this sooner... must have put on and pulled that jumper off 100 times...
Now, the symptoms were those listed in the manual as graphics failure i.e. one long and two short beeps. This was with an athlon x2 5600, which I'm not sure what core it is actually down inside, it could be that it is too new for revision 1.1.