Problem with Artwork

Hey guys,

I have recently started running into a problem with the files appearing in my iTunes library. I recently purchased an Airport Time Capsule and have moved my iTunes folder onto an external hard drive which is now connected to my Airport. Everything still shows and is accessible via iTunes, just the files are stored remotely. It was fine for a couple of weeks, although now I am noticing that various movies and shows (not all of them) are missing their artwork. When I right click and get info, it shows all of the data still, and when I then click OK the artwork immediately shows in the library.

The annoying is I have to do this for each individual show and movie that is affected, and it seems to take ages. I know it isn't a breaking glitch, but I am really anal about having the correct artwork and information for each of my files, whether it be TV show, Music or Movie. Does anybody know how I can prevent this from happening, or at least why I am now experiencing this problem? On a side note, these are MP4 files I have added to my iTunes library, none have been downloaded from the iTunes store.

One other thing, I am unsure if this is related but I though I would post this here prior to making a new thread -

I watch this content by streaming it to an Apple TV. Again, things started off fine but now when watching something, the sound disapears after about 25 minites of watching said video. If I hit menu and reselect the video, sound is there as perfect but again 25 minutes later the sound goes out again. This doesn't seem to happen when watching directly on my Mac Book Pro. Are my two problems connected? Is this an issue with the Airport Time Capsule perhaps?

Any assistance that can be provided would be most appreciated.

Many thanks,

Rikki