Jim
Just a basic setup that would make a huge difference if set wrong.
> iTunes > Preferences > Advanced Tab/Icon > uncheck "Copy files to the iTunes Media folder"
With this setting, you are only indexing the files not copying them to your local hard drive.
Otherwise you would be copying all the files to your local iTunes folder
and that would continue until your hard drive fill up.
I think that by default the box is checked which you would not want.
Also you could try to import a sub set of your data like a folder with just a few items
and see how that works. You can always delete these item and re-import them later.
The basic idea is in iTunes:
iTunes > File > Add to Library ( Select your media drive ) This could take awhile.
perhaps this is what you are doing??
I have not had much luck with NAS drives, but some folks do.
These drives will only run as fast as your network, so if you have any network problems,
it could cause skips or dropped frames in your videos.
Sounds like you are throwing a heavy load on a slow connection.
I use a dedicated Mac Mini with a 3TB firewire 800 drive attached for my media.
Then I can share the iTunes library with other iTunes computers or do some streaming
to iDevices via Air Video or Streamtome apps. (this requires a server piece running
on the computer with the iTunes Library)
If you just want to do music, investigate PulpTunes. It seems to work well thru a browser.
If your media is not compatable with iTunes, it won't import the media.
Examples: wav, wmv, avi, etc....
Just try a single file from your nas and see if it comes in.
I have converted all my media to iTunes format but still occasionally have issues.
Hope I helped.
Keith