I found this method work flawlessly for me:
If SLAX 6.11 successfully detected your wireless card, but you are strugggling with Kwifimanager to connect to your WEP protected wireless router, here is the steps:
1). Start Kwifimanager, click on the "Scan for Networks..." button;
2). If your WEP protected wireless router is found, click on the row which shows your wireless network name, you will find that the "Switch to Network..." button is greyed out (disabled), because you have not typed your WEP key yet;
3). Double click the cell in the WEP column of the same row, remove the "on", key in your WEP key in the cell completely, after you hit "Enter" key, the "Switch to Network..." button will be enabled, click on it to connect to your wireless network. If you type all the key right, it should connect;
4). But the internet does not work yet, we need to get a IP from the router. Open a shell, type "dhcpcd wlan0" (wlan0 is my wireless interface), voila, in my case, the router assigned an IP to my notebook, you can tell from the "status of active connection" window in the Kwifimanager.