I had some initial issues with the box seeing my MKV's on a network shares via ethernet, it did see the share but instead of the up to date content it was seeing previously deleted stuff, an issue i fixed by re-indexing the shares on my server using windows media player, a simple fix.
I can now play the MKV's on my network share, however I have no sound when viewing these, anyone have any ideas how to work around this issue? I can confirm that the MKV's have sound when played through another source.