wireless networking with bt voyager 2000 router

I have setup a small home network (wireless) via ethernet cable via router.
I have given the network a name, shared key, 64bit WEP on channel 7, when I
apply the same settings to my laptop It shows a little icon in the taskbar
of a pc with a signal radiating from it but with a red cross, and it says
not connected. However when I try to access the internet I can, only for a
limited time before it says network problems. I am using a pB Eseries
notebook with an intel pro wireless lan 2100b mini adapter. Now I seem to
remember that there is a method of turning this on and off but I cant
remember how to do this. It is by using one of the keys on the keypad but I
cannot remember which one.