My D Link 323 NAS box worked perfectly under xp but with a dual upgrade to a Billton 7300 router and Windows 7 I have had continual problems.
After applying all the latest firmware to both devices I got it sorted
The final niggle was the 323 could be set up with mapped drives but I was randomly loosing my mapped drives when I shut it down. I could ping the NAS box and read the administration page and see the media server but could not access the file system via my mapped drives or device name ie \\NAS\Volume_1\
The solution turned out to be to use the ip address rather then the divice name in all mapping or accessing the device directly ie \\192.168.0.5\Volume_1\
This has been such a pain in the bottom I thought I would past it here - if someone is searching for the same problem they might pick it up.
