Just wanted to share my experience with the community.
Was fiddling around with a WD MyNet N900C (2TB) to connect to my home network (a friend got a bunch on sale…). Configured it in AP (Access Point) mode as I already have a working home network.
When I loaded some videos on it and tested it, I found out that there were no problems playing back videos from Windows PCs (via SMB share \WDMyNetN900C\Public). However, when using XBMC running on various platforms: OpenELEC HTPC (IONTop), Android Tablet (Asus Transformer Pad TF300T, and MINIX Neo X8H-Plus (Android media player), they all encountered problems playing large mkv files. BTW all these XBMC devices played the same videos just fine from a Windows shared drive.
I tried other video formats and found that the XBMC player could play MP4 files over the WD MyNet N900C SMB share. After hours of research and fiddling, I found a workaround.
Obviously, the problem has something to do with the interaction of the XBMC SMB client with the SMB server built into the WD MyNet N900C (a custom Samba build called KC_SMB). Since I have no expertise to fix this problem, I used another protocol to share the files: FTP.
The WD MyNet N900C supports sharing files over FTP (in addition to SMB, DLNA, and iTunes). I just activated the FTP sharing, and created a connection in XBMC to the WD MyNet N900C using FTP instead of SMB and VOILA! MKV Streaming is working properly now.
Hope this workaround helps others having similar problems.