I use XBMC, but also tried with VLC and I get the same problems, plus pixelation of the image when it freezes.
I tried with a newer MacBook aluminium unibody, and the same thing happens...so it's not the Mac, it's the TC.
I think that even if I will buy a proper NAS with Gigabyte port, I will get the same results. The only NAS that would work flawless I think it woud be one connected via Firewire 800.
I have cat6 all over my network, but the result it's crappy. 720p movies works just fine, but 1080p DOESN'T.
I think the only solution to have a proper HTPC with a movie colection, would be to buy an iMac or a Mini, and connect it to a firewire NAS, not gigabyte ethernet.
Did ANYBODY tried a Mini or iMac with an ethernet gigabyte NAS (like Synology DS411j or Drobo FS), and got good results (playing a 1080p movie the same way a blu ray player would play...without pausing and freezing)?