I have the same problem using the Mediaplayer.
DVDrips are places in a SMB share on a NAS in the following structure
DVDrips is done using AnyDVD and CloneDVD.
When browsing the share metadata and covers is fetched without problems but when I press play I get the playback error.
diagnostic Serial C07G6BH9DDR5
ATV ver: 4.3 (2557)
OS: 4.3 (8F455)
I have done a quick test. When the movie is placed on either of my NAS (Freenas or Qnap) i get the error but when I copy the same movies to my homeserver playback is okay.
Could be a problem accessing smb shares or maybe a security problem. I think my SMB shares i read-only. But when testing on the homeserver I had full access.
Will do some more test later.