I recently added a new PC running Windows 7 and I have both created new content and migrated existing content to it from a Windows XP PC that is working like a champ with Windows Media Player service and the DSM-520. When trying to play files from the Windows 7 PC on the DSM-520 I get an "Unable to open file" error when I try to play some avi movie files, but not all of them. Music mp3 files play fine. I do see an error in the Windows 7 System event log:
The Windows Media Player Network Sharing Service cannot process the request for URI 'http://192.168.1.118:10243/WMPNSSv4/1502456120/ezg4MkIxRTQ1LTk1MzgtNENFMC05NzdDLTA0QjJBNkRCRDI4MX0uMC5GNjRGNTIzMw.mpg?formatID=31' from IP address '192.168.1.101' due to error '0xc00d1967'.
Unfortunately error c00d1967 is not documented anywhere. I've been over the file permissions with a fine toothed comb and they seem fine.