Stable: 2.5.2
Development: 2.6-alpha3
I don't know it this is supposed to be a desired behavior, but after I unmounted my music folder (located on a sambaserver) and restarting moc, the previous playlist was still loaded and after trying to play its first song, mocp gave some error messages about not being able to load those files. That's okay, I guess, but instead of being able to clear the playlist all of my input (shift+c, q/Q) was just ignored and moc succeeded to try to play the files from the playlist.
This should'n be a samba problem, though you might want to reproduce this "bug" like this:
1. mount a folder with music on /path/to/mount
2. start mocp, add some of the songs from /path/to/mount to the playlist
3. (I guess SavePlaylist option has to be set to Yes) quit moc (shift q)
4. unmount /path/to/mount
5. start moc and play a song from the playlist