Hey, while using MTP mode I had a problem that may be an answer (but not a solution) to this: Several times I changed the tags with Windows Media Player and if the songs were already in the Clip they didn’t get updated. I dragged them again to force an update and this worked only sometimes. Other times WMP said ‘Updating information’ (or something like that) when synchronizing but when I went to see what was in the Sansa the songs still had the old tag. Sometimes even the tags of the Clip files said one thing from within WMP and another thing in the Clip screen. I tried to update manually with WinAmp, but I think it was worse.
The bottom line: I went (back) to MSC mode, batch-tagging with mp3tag and updating (comparing) the contents with TreeComp (it’s a great application, BTW).