I'm not sure if there are some other reasons people are having these problems. But do you all have your routers setup to issue the same IP address based on MAC address? This prevents your LAN IP's from changing during reboots, ect. So every computer/device will always get their same IP.
it should work wirelessly/wired as long as:
1. all your devices have has static IP's on your lan
2. setup your PS3 correctly
3. you setup your dns server correctly
4. you allow devices to talk to your dns server via the software firewalll on the pc running the dns server
i've got my Simple DNS server working just fine, using WiFi on the PS3 and it also works with my dlink DGL-3420 wireless nic adapter. Haven't had 1 issue getting the ps3 to communicate with the DNS server.