Trouble connecting to wireless network.

I have a linksys router. It had WPA on it and one computer was working fine the other could connect but couldn't get an IP.

I decide to make the network unsecured, the one having problems is now ok, connects gets an IP no problem. The one that was working without a problem now has issues. If I reboot it it will connect, it shows excelent signal quality then all of the sudden it will disconnect from the network and when I try to reconnect it fails to connect even though it has a nice signal.

What is going on? Why would it connect without a problem when the network was secured yet not work at all when it's unsecured? It's on the same channel and everything.

Reset the router to defaults, button on back.

Run the network setup wizard on both use the same network name on both, give each computer a different name.

All should be good.

Confirm that WPA and any other security settings in the "one computer" has been removed/disabled.