Thanks for the tip but I must point out that the latest firmware, for the Linkstation Duo LS-WXL/E is version 1.4 which had a post date of 28 December 2010. The first thing I did, after I bought this puppy, was to update the firmware to this latest version even before transferring my media files from my old NAS and reconfiguring to run as RAID 1 (I've lost data on previous NASs before so I always configure my NASs for RAID 1 nowadays). As reported in my post, my .mkv media files do not play on this NAS, despite running on the latest firmware, even though the same files work over another DLNA software running on my Mac which is TVMobili. If I compare the LinkStation Duo's DLNA software to TVMobili, I must say that the former is rather rudimentary as it does not even support the basic Pause, Forward and Review buttons on my Samsung Blu-Ray BD-C5500's remote. Once I start playing a supported .avi file, I would have to play it right through to the end as there is no way I can resume from a previously paused location. This is rather annoying so I end up not playing media files off the LinkStation Duo NAS but have to turn on my Mac and run the TVMobili software most of the time, certainly not what I had intended when I bought the LinkStation Duo NAS!