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.