Hi,
Actually, there is a specific forum for the DNS 320L
http://forums.dlink.com/index.php?board=347.0
Dlink's placement confuses a lot of people. Might get better results there. I do not think your 3TB drive has anything to do with your issue, I know I have seen some rare problem similiar to yours though in either this forum or perhaps the DNS 325 forum. You might get luck searching different key words. Good luck