Actually, whoever posted that it was easy for them to get DLNA media server working has no idea what they are talking about or what constitutes DLNA media server or for that matter even a file server, but let me explain.
DLNA media servers are meant to be able to inter-operate with DLNA media player clients, most of which are not capable of full access to the file system, SMB abstracted or not. In simple terms, devices like your TV have a very light-weight client (player) built in that is DLNA certified and as such it is programmed to access only DLNA media server content organized in a very specific way. Typically, what a DLNA client will look for is media "libraries" such as Music, Videos, Photos, etc. being served to it in a specific way. Now, the RT-N66U does report these "libraries" to DLNA clients, but there is no way to manage the said libraries at all, and they in no way link back to the attached storage. In fact they link back to nothing at all!
Now, a file server is any server capable of "serving" files across a network (yes, the definition in essence is that dumb). All file servers are in principle media servers as well, since they can offer access to media content to those clients capable of accessing the same file server shares. However, most file servers are not DLNA media servers, since they offer no DLNA certified interoperability with DLNA clients. Simply put, while they are capable of serving files they do so using the standard SMB protocols (for instance). This however is not recognized by light-weight DLNA clients and therefore they are unable to actually access any content. The fact that you can access your media files over a network using a network enabled device != DLNA media server...not even by a long shot This also does not imply in any way that the DLNA media server capability is working on the RT-N66U.
So, again, we are back to square one. DLNA media server on the RT-N66U does not seem to work at all, and the SMB file serve is very poorly implemented.
Edit: I will be doing some tests tonight with the files dumped into the root of the drive to see again if that will make any difference, particularly with different file systems.
have you tried tomato