lol
*All this is written assuming you made an upgrade and not a fresh install*
This usually happens after an kernel upgrade. What you have to do is copy ipw3945.ko to
/lib/modules/'uname -r'/kernel/drivers/net/wireless/
Where to get the .ko?
Download ipw3945-1.2*.tgz from
http://ipw3945.sf.net
hit the make command
To configure your WEP connection type in system-config-network and then select your wireless interface and configure it.
Generally the wifi interface is the eth1 and not the eth0 (ethernet - lan) or l0 (loopback)