I had a linksys wired router hooked up to my laptop and it worked fine. I bought a new TrendNet TEW-639GR wireless router to replace it and followed the following steps:
1) I replaced the linksys with the new trendnet and hooked up as before
2) I checked my laptop and it worked fine via the ethernet cable.
3) I setup the wireless with WPA2 and was able to connect to the wireless network. I disconnected the ethernet cable to test that the wireless worked and it did.
4) Later in the day, I retried connecting the ethernet cable and got a "Limited or no connectivity"
5) I tried wireless again and it still worked perfectly
6) I restarted the laptop, router and modem but that did not fix it
7) I checked ipconfig and I was getting a 169 ip on the ethernet, the wireless would get the right 192 ip
8) Given that the router had worked properly initially, I reset it back to factory defaults by pressing on the reset button for 30 seconds
9) I tried to connect via ethernet again and it did not work, same ip problem
10) I tried wireless (now unencrypted) and it still worked
11) I checked the properties of my LAN connection to make sure it was set to automatically get IP and DNS, it was set correctly
12) I do now know what to do!
Today I will try with another laptop to isolate the problem. One more thing, I have a NAS connected to one of the LAN ports of the router and is accessible via the wireless network.