Saving WEP Key

I'm running XP SP2 on a Dell Laptop. I connect to the Internet via Cable and

an encrypted D-Link Router. Up until several weeks ago, My connection was

automatic. All of a sudden, my wireless will not connect automatically. but

does detect a wireless source. When I go to the Wireless Network Connection

screen, I'm told that the connection requires my entering a WEP key. When I

enter the appropriate 10 digit number, it connects with no problem.

I've checked everything I can, and the appropriate WEP Key is stored, but

I'm still asked to enter it manually each time. I never had to do this in

the past. Any help would be appreciated.