Why won't PSP connect to WEP anymore?

We have had a PSP for about 2 years. All of a sudden, earlier this year, it stopped connecting to the wifi. Finally sat down and have tried different things. Reset the router and tried a WPA connection. PSP connection works (but we don't want WPA in the house, we want WEP). Change it to WEP and all other devices work with the settings, but not the PSP. It actually finds the IP address now (it wasn't before), but when it tries to test the connection: "A connection error has occurred. (FFFFFFFF)

Why doesn't it have a problem with the WPA connection but does have one with the WEP? Yes, I've deleted and started a new connection, checked the WEP key...