Did you configure iTunes/last.fm before or after importing your library? If you did it after, then that's the problem -- you'd need to perform a full reindex using:
/usr/local/centovacast/bin/ccmanage reindex USERNAME --updateall
If you imported after configuring iTunes/last.fm, then for some reason it's not able to identify the track on iTunes or last.fm. You can troubleshoot that by running:
/usr/local/centovacast/bin/ccmanage serverdiagnostic USERNAME getalbumdata --file=foo/filename.mp3
Replace USERNAME with the username for the account, and foo/filename.mp3 with the filename of one of the affected MP3s relative to the media directory. eg: if the filename is /usr/local/centovacast/var/vhosts/USERNAME/var/spool/media/rock/myfile.mp3, use: --file=rock/myfile.mp3
That should tell you in detail which drivers it's trying to use to identify the file, and what result it's getting from each driver. If it's unclear, post the output here for help in deciphering it.