Hi,
i've a DNS-323 with firmware 1.10 .
I've a SmartTV 7 series with DLNA support and network adapter, but my nas doesn't support DLNA natively so i've installed Funplug 0.7 and some others tools and now i'm "root" in my NAS with NFS DLNA etc etc like services.
Now it's a really linux machine and it's able to stream to DLNA devices capables and my TV can read media contents from it.
The network access it's like a PC-NAS and the speed the same, and if you got all WIRED the connection time is fast in connect and load.
So i don't know how help you because your NAS is different from mine (in software) and i use a Samsung TV like client this could mean:
1) IF your problem is NAS side (backup all first or detach 1 HDD if you got raid, then upgrade firmware, install fun_plug 0.7, install twonkyserver 7 as DLNA STREAM server) to got a NAS like mine
2) IF your problem is DVD side (try to upgrade it's firmware or search for connection issue in other cases)
Regards