If it helps for info, I've got a Thecus N5550 that was using four 3TB drives and I pulled MKVs over my network with MC18 no problem. I did a simple map network drive to a drive letter and that worked fine.
I'm in the process of upgrading to five disks and am changing the RAID level, so it's having a long hard think right now.
I'm thinking of setting up using iSCSI to (I expect) improve network speeds. This might be an option for you that could possibly help. I don't know. I'm a dabbler, really.
I suspect there are more elegant ways of skinning the cat but in my case MC talking to my NAS has worked without difficulty.
One thought that comes to mind is that some NAS makes include a media server module like Twonky (I know Thecus does but I don't use this functionality as MC does a sterling job). Do you have that option and can you pick up the Twonky DLNA server using MC, as an alternative?
The other thought that I have is this - what format is your LAN connection? WiFi? Or via ethernet cable? My setup uses an ethernet over power communication, that's an alternative to a dedicated wired up option. I know that video over my wifi at home can be problematic. Via a cable (even one that carries appliance voltage) - no issue.
Hope you resolve your hassles soon.
[Edit - you probably should have posted on this discussion board
http://yabb.jriver.com/interact/index.php?board=7.0Your post's subject heading is rather general. I've thrown up a suggested heading to prompt the flow of your creative juices]