WEP wont work! i need help!

the internet on one of my computers on my network
suddenly quit working the other day. so i reintalled the
broadband utility because nothing else would work. but
now its telling me that when i try to type in my WEP that
it is incorrect, but i have check it more than enough
times to know that that is the correct code. what do i do?
oh and i have changed it to something simple and it still
didnt work even when its too obvious to get wrong. please
help meee!