I had the same problem on my new p5b. At the suggestion of folks on this list, I added another NIC. That also didn't work with my FC 6 installation. (No driver for the card!). I got the latest kernel rpm through my windows box and installed it on my FC 6 side. The new kernel had the correct driver so now I'm up and running.
From looking around at other postings, I see that probably things may
have worked if I had let the system boot without having it connected to the net so the card could be detected properly. Maybe... Anyway, I'm up and running now. LOL. -Tom
