Hi isiv,
As you rightly mentioned by you the issue can either be with the motherboard or the graphics card. I would suggest you to clean the graphics card slot thoroughly and ensure there are no dust particles. You may update the system BIOS. Please refer to the link: http://dell.to/147tT1P. You may try using the graphics card with any other system, if possible.
Keep me posted with the results. I will be glad to assist further.