Aha! Is it your GoList that is getting hijacked?
Be suspicious of Windows Media Player (Rhapsody uses some functions of WiMP, as it pipes DRM files to your device). I had an interesting glitch about a month ago: WiMP literally stole my Rhapsody Channels and turned them into playlists.
The result was that Rhapsody could no longer access them. The R4 client saw playlists, and no Channels, even though I could play them from the Clip.
I wasn’t using an active GoList at the moment, but if I recall, WiMP suddenly had a GoList in the library.
Try the combination of reinstalling the firmware on your Sansa: the beauty of the Clip is that it behaves like a hermit crab, taking the new firmware file from the root directory, and reinstalling the firmware quite transparently, without affecting your music files. See if a new copy of the firmware helps, as in my particular case, WiMP goofed up the wee Clip’s file structure. I had duplicate Music and Rhapsody file folders, among other things.
It’s a great idea to always back up your music files on the PC, or at least have easy access to them, so that in times of frustration, you can always perform a quick format and start on a clean slate.