I have been using My Movies for a while now. I am using the Windows Home Server version. My Movies for Windows Home server allows you to keep all of your movies on the server, and play them back in Windows Media Center. This has been working great. I have been having problems with playing the movies on the Media Center Extenders
The first problem is that the cover art doesn't appear. Then when attempting to play the movie, an error would appear that the file could not be found.
This thread on the My Movies forum describes the steps needed to fix the thumbnails on the extender. I found a similar solution that fixed the video files. I RDP'd into the Home Server and then went into the "Sharing & Security" setting of the share that has the movie files. In that setting page I made sure that both "Anonymous Users" and "Everyone" has read access to that share. Once I did that, everything works great.