Swannque,
I don't have JRiver yet, but I have a question that is unrelated to the media software you are using. What speed is your network? what speed is the NAS's network card? You should be able to stream HD video from a server over your network without problem. I don't have BD's but I do have a HD camcorder and have had no problem with viewing them over the network, even before I switched to a gigabit switch and upgraded the HTPC's mobo to include gigabit.
In the past, though, I did have some latency issues with a NAS. Some just don't seem to be as snappy as a true server. Maybe that has changed recently.
If you have another computer on the network, you may want to try putting one of the files over there, sharing the drive and see if the issues you were seeing persist. If it does, then you may have some kind of network issue (but make sure the computer you are using has a fast hard drive-not a 5400rpm jobby). If it doesn't, then it's obviously the NAS. It could be the hard drive, or it could just be the internal hard ware.
Lastly, you really never should rip something to a networked folder. There's too much room for errors to creep in. Obviously you see how much it slowed it down. Ethernet has a lot of overhead to ensure the data is correct.
The NAS should be fine for serving/backing-up files, photos and music though.
Good luck.
hEdly.
