iTunes match issues: Apple Support Communities
iTunes Match hangs on Steps 2 or 3 when your music library contains mixed media formats (MP3s, older AAC files, or protected files) instead of uniform unprotected AAC 256 kbps files—a software bug that leaves files stuck in an endless loop rather than marking them ineligible. Convert all non-compliant files to iTunes 10.5.1 AAC 256 kbps encoding using smart playlists or individual selection, then delete the originals from iTunes, your computer, and iCloud before re-running the match. If Step 3 still hangs after converting all files, the problem is likely a firewall or modem blocking the upload port, which you can identify in Activity Monitor's Open Files and Ports window and resolve through your modem's settings.