Your camera is on the list of supported cameras for the latest DNG converter. It is also on the list of supported cameras for Camera Raw 6.7, which was the last update for Photoshop CS5. I cannot confirm that support because I don't have a D800. Is the DNG converter that you have the release candidate or the beta version that was out at one time? You might check for the latest updates and see if that makes a difference. I would also recommend that you update to Camera Raw 6.7.
Thank you Jim. I DL'd Camera Raw 6.7 and can open raw files from within Photoshop. You solved my problem.