Comment 10 for bug 147883

Lexual, if it is in fact this bug that is causing your import errors, manually importing the folders should work properly. The issue is just with automatic importing.

I've also discovered that by re-selecting the Music Library location in the Music tab in the Options window, the problem stops occurring. You don't even have to choose a new location; just click Browse, select your music folder, and close the preferences window. I suspect the problem stems from a bug in interpreting a configuration file created by a previous version of the program.