Vista, Mapped Drive, and Offline Files

I use a NAS to store all my media files (as well as backups, etc.). I share these files among multiple computers so I the share mapped as the M: drive on all the computers. This allows me to store the iTunes Library on the share, and have it work from any computer.

On my M: drive I have Music, Pictures, and Video folders. I have the Music folder set as available offline so I always have access to my music library. None of the other folders are available offline. This works fairly well, except recently when I return home Vista won't reconnect the M: drive. I can navigate to any other shares on the NAS, so I'm connected and authenticated, but something is prohibiting Vista from reconnecting the M: drive. It just shows the Music folder but the other folders are 'unavailable'.

I don't have any idea how to 'force' it to connect or track down what could be causing the issue. If anyone has seen anything like this, I'd love to hear some ideas.