Rather than a bug, I find this as a strange behaviour of two installations of Muscibee, one on a portable device and the other one on the desktop computer. There are times when I would need the two installations open on the same computer. I found out that I can carry tracks from the desktop installation to the portable installation but not vice versa.
There are times when I would like to duplicate the playing list on the portable to the desktop but with this restriction, it cannot be done. Is there a solution other than having to compile the playlist again?