I have tried MSC which gives empty Play Lists and MTP which give nothing, both give extra copies of the same song...
I have set \Music\<Album Artist>\<Album>\<Title>
I have set \MUSIC\<Album Artist>\<Album>\<Title> just in case
Tried "Sent to..." and Auto Sync to get them on the Clip
With the settings of "Force relative paths" and Library Playlist"
No luck on any combination? This is on Windows 7 Pro x64, MM 4.0.3, Sansa Clip 4GB, also tested on a Clip 2GB and a Clip+ 4GB...
Worked without changes to CLip of MM when I was on version 3.x.
The only thing I can think of is your Playlist destination; is it ? \Playlist\
And in Option>Auto-Sync do you have Delete files and playlists not included in auto-sync list from the device checked?
I am so surprised at all the issues with a Sansa; I must be blessed.