In your Realband folder, look for the PTW Pictures file.
See if you have pictures in the folder for Audio Pictures and MIDI Pictures, in each of those folders you'll have to look in the Factory Pictures section. I believe the pictures are necessary.

If they are there, can you create a new Category?
If not, I gotta believe it is still an indexing issue. Is indexing on for the whole drive? I'm thinking in NTSF format it would need to be on for the whole drive, not just the folder.

Are you running RB from the external drive, or on your system?
Are the realtracks on the external drive or on your system?

These may be clues.

I do not work here, but the benefits are still awesome
Make your sound your own!