12.04 Wireless network asks for WEP key every 5 minutes, Please Help
I had the same thing happen to me on a dist upgrade from 10.04 to 12.04.
The wireless worked fine in 10.04 then after the upgrade it kept asking for the wep key every 30 seconds. But the network would work in that 30 seconds. Frustrating. I found this answer and found a bit of a faster way to get things going.
First, open up the drawer, type in Network Tools. Then open Network Tools, switch it to the WLAN and click Configure. Finally in the Wireless tab, find the "auto" connection, highlight it and click Edit. then go to Security, and enter the key there. Click Save and it's done.