Yup- I had the same problem when trying to map a drive using the not so easyshare utility. It prompts for credentials and nothing seems to work. Yet when you try mapping the old fashioned way: (in a DOS console type the following: net use * \\(insert DNS-321 IP address)\Volume_1 ) it works just fine.
I just bought this unit and after getting frustrated with the easyshare utility, figured I try the forums. What a disappointment to see all the negative responses especially about firmware... I'm just glad I'm not the only one that encountered this issue. Truth be told you get what you pay for, and as this was one of the cheapest diskless NAS units offered on newegg, I'm not that surprised that everything doesn't work flawlessly. It's actually nice that they at least attempted to provide a GUI app for mapping drives- the interface, if it actually worked, would probably be easier than the Windows GUI method. Until they fix it though, the command line method is probably the quickest.