Problem with Syncing music from Windows Media Player

I have loaded some CD’s onto my laptop and synced them to my Sansa Fuze.  I have done this a few times.  Last night, I ripped some CD’s again and tried to sync them to the Fuze.  I got this message:

“Windows Media Player cannot access the file.  The file might be in use, you might not have access to the computer where the file is stored or your Proxy settings might not be correct”.

Well the file is not in use, except at that moment to sync the music over.  I have access to the computer - it’s mine, no other passwords or anything required.  I have no idea what my Proxy settings are or what they are talking about there, so that might be it.  Has anyone ever got this message up and what do I do now?  

I have WMP 12 and the only time I have ever gotten something like that on ANY operating system was when a song was locked from me. To change it try going to WMP or control panel and changing permission settings.