Actually, I just had this same problem with my new X70 mobo and GTX 780 card.
The problem is similar to what was outlined above, but with a twist. The bios on your mobo doesn't support the new cards from the 700 series. It's a simple fix though. Pop in an old card and you'll notice that your system starts np. Then go to the Asus site and grab their most recent bios for your mobo. Update it ( carefully ), and them pop back in your Titan.
If you do use an old gpu for the bios update, make sure you try and use an NVidia one so that you don't end up with ati drivers to uninstall later.