Change to WPA or WPA2.
Here's why. WEP has a nasty issue that it will do EXACTLY as you wrote for many reasons. WPA or WPA2 will cough and tell you why it failed.
I can see you have the caps lock on and that can cause no end of WEP service calls. WPA and WPA2 fixes that issue.
Bob
I RECENTLY UPGRADED MY DELL INSPIRON 9100 LAPTOP. I SET UP A NETWORK USING MY HP DESKTOP AND TRIED TO USEE THE LAPTOP TO ACCESS THE NETWORK THROUGH THE WIRELESS ON THE DELL LAPTOP. MY FIRST ATTEMPT WAS SUCCESSFUL, BUT I REALIZED I HAD DISABLED THE SECURITY. AFTER SEVERAL ATTEMPTS TO USE THE WEP SECURITY, I FINALLY HAVE MY LAPTOP SAYING THE SIGNAL STRENGTH IS EXCELLENT AND THE STATUS IS COONECTED TO THE NETWORK, HOWEVER, I CANNOT SIGN ONTO THE INTERNET. ANY SUGGESTIONS? THANK YOU.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic