Ive see the behavior that you are experiencing when there is a compatibility problem with the graphics card installed. Sometimes adding another card will slow down the POST sequence and allow other cards to be recognized properly.
At this time I recommend you to look in BIOS for the expancion card text option and change it to see if it will improve your video card recognition.
Please note that it is recommended that you have the latest BIOS on the motherboard and latest firmware on the video card.
Thank you very much for your reply, your explanation makes sense. I have upgraded to the latest BIOS, and since this upgrade the graphics card is now being detected properly with no problems.
Thanks again for your help!