Recently added and watching keeps going blank

Upgraded to 7 and when I add or watch a film, the artwork shows, but I can go vacuum next day and all the artwork has gone in those sections. The posters are there in the library for all the movies. Any ideas?

What protocol are you using to connect to your server? SMB, FTP, UPnP, DLNA, etc

SMB protocol

When you say blank, do you mean that there is nothing there or is there a blank poster where the artwork should be?

Sorry, yes, blank poster

Have you tried doing an edit metadata and re-selecting the correct name to see if it would refresh that way?