Can't 'Get Info' for iTunes items stored in my NAS

I've recently moved all of my music to my Sinology NAS - I've managed to get all of the music backed up to one folder (using the consolidate option from iTunes) and have found the music in the NAS by redirecting iTunes to look for the NAS folder - all of the music is there and plays, however when I try to highlight multiple tracks and then 'Get Info' from the File menu (to sort out complications etc) the menu is greyed out?

Any ideas?

Thanks,

Chris.