You can download your logs from control panel and check "nextsong.log" to see what happened.
I've got sometimes something like this:
2013-08-22 05:07:37 Error submitting HTTP request: Receive failed: Connection timed out (-5)
2013-08-22 05:07:37 Falling back to local sequential playlist: /usr/local/centovacast/var/vhosts/account/var/run/playlist.last
2013-08-22 05:07:37 >"10.0386","static","/usr/local/centovacast/var/vhosts/account/var/spool/media/midnight-ride.mp3","","","","","0","","","OK"
I don't know why that is happening but it is occasionally and after this everything is going back to proper playlist.
In this log you can see what playlists was playing in specific time.
2013-08-21 22:36:51 >"0.0319","database","/usr/local/centovacast/var/vhosts/account/var/spool/media/danosongs.com-joy-in-land-formation.mp3","Dan-O at DanoSongs.com - Joy in Land Formation","Dan-O at DanoSongs.com","Joy in Land Formation","","0","577","Heavy Rotation","OK"
This is before last parameter - "Heavy Rotation"
I've hope that helps