I have one of the first Link Theater PC-P3LWG/DVD, I've had it almost 5 years with no problems. I'm also connected Ethernet, who set up your Ethernet was it all tested properly (568A?) Did you set it up according to the Link Theater Manual, and are you using Link Theater Software? I did upgrade my Firmware, I think it is 08..... Something but I don't think that is the problem. Something is not connected properly if you lose connection or it locks up.
I have DVD Movies back-up on my PC in my computer room and Server in the garage and I can stream them to my 62" Mitsubishi HDTV with no problem.
I went into my Set-up and looked up some settings, my Firmware is below:
Go into your Set-up and tell me what you have under IP, should be your IP Address, Subnet, Primary DNS, Secondary DNS, and Default Gateway. Let me know if this is what you have.
Then under Network:
Network - Wired
AOSS - On
SSID - Buffalo
Conn - Infrastructure
Wep - Disable