Positron doesn't properly handle directories and files that end in a period.
While Positron intelligently handles invalid characters, it misses a corner case of FAT: files cannot end in a period. I discovered this after putting Enigma's 'MCMXC a.D.' on the Neuros; the database said the music was there, but the files wouldn't play, and I finally realised it was because, on the Neuros, they are in a directory called 'MCMXC a.D' . . . a subtle but important difference. This should be really easy to fix.