Serato Itch Problem! Any Advice??

Could be various things:
– iTunes songs with DRM? (Itch cannot play them)
– Wrong sound file format (Itch cannot play all formats)
– Your iTunes library is corrupted
– You are using iTunes below version 6
– You are using a PC and your file system permissions have a problem
– You are using a Mac and OmniCleaner and it destroyed your library
– Your Itch library is corrupted somehow (read Itch manual how to do a total re-scan)

These are the ones from the top of my head.