N68C-S-UCC Boot problems with video card

[veritas]

I have recently rebuilt PC using the Asrock AM2 N68-S-UCC and have it running Win 7 64 with no problems. I decided to add a graphics card to enhance performance but as soon as it is installed the machine wont post with no output to the monitor. I have trawled the internet and have noticed others having the same problem but havent seen any solutions.

any help or guidance would be gratefully received