Here you can find a bit more explanation:
http://wiki.dns323.info/howto:bettersamba#how_to_make_the_dns-323_work_with_unc_pathsPlease be ware this particular section is talking about 1.03/1.04 firmware, which still applies till 1.07, but apparently had been changed in 1.08. For a matter of fact to resolve this issue it's recommending same Samba configuration change as D-Link did in 1.08 (probably D-Link got this idea from this wiki

)
I didn't investigate more about this issue, one thing very obvious is in 1.07 style sharing while accessing Nas Windows asks password only, user name field is grayed out, I guess which means if you are not using the user name that Windows assumes then likely you won't be able to log in (unless you map it as a network drive). On the other hand if you have only one user configured on Nas then it's possible that you won't see this issue, for me since I have multiple user accounts configured on my DNS-323 with different privilege I guess that's why I'm seeing this issue in 1.07 style sharing. Again, it doesn't really bother me much.
I still believe it's a good idea to make it configurable through web UI, really everyone has different needs, and really it's just a simple samba configuration change (please, correct me if I'm wrong).