I just noticed that all my Real Tracks are showing as N/A, even though they play when loaded. I checked to see that they are in the file C:/bb/Real Tracks and they are present and do not appear as N/A. Is this an installation problem?

Try performing a Rebuild in the StylePicker.
You could also do this in the RealTracks picker, but I think that the StylePicker does both.

I've also found that sometimes fixing this requires me to run the "Rebuild and Fix" option in the "Realtracks Picker Dialogue".