songbird does not keep imported songs in library

i've imported songs from a directory where i keep my completed bit torrent downloads (if that's relevant) and then i have set up that directory with the media importer plugin. and it works great, but after i quit songbird and a day or two pass, i'll notice that all the songs i have imported have been lost and i have to restart the whole process again.

but if i restart songbird after only a few minutes or so, it is fine, i have no problems. the problem only happens when i seem to start it up the following day.