ATI TV Tuner 650 detects zero OTA ATSC channels after scan

Does anyone with an ATI 650 PCIe tv tuner have any experience with the tuner not receiving any OTA HD channels after a scan? I have confirmed signal reception on the line with a TV as I have a 110" roof mounted amplified antenna with 30 mile direct line of sight to NYC. I can collect all NY Broadcast stations from every TV in my house so I don't believe signal strength/quality is an issue. Additionally, I have confirmed that I am using the ATSC jack and not the NTSC jack (NTSC works fine). I have downloaded the electronic Program Guide as well since i've heard that not having it caused other tuners such as Hauppague from receiving. Is there something that I am doing wrong? I have already returned one card already so I'm on my first replacement card. The behavior was identical with both, so I imagine there is a setup issue? I am running WinXP SP3. I have also heard other tuner brands have issues with systems running 4GB RAM or more. I have 4GB but since i'm running 32bit O/S, I imagine its not even addressible so a non-issue... Does anyone have experience with this? It would be much appreciated. Thanks!