I just got an Arduino wifi shield R3 that I am trying to get working with my Arduion Uno R3 on my home network. The router is a netgear WNDR3700 and it is using WEP encription. I have replaced the ssid, key and keyIndex in the ConnectWithWEP example. The serial monitor prints: "Attempting to connect to WEP network, SSID: R467g47pQm" and then the error LED comes on on the sheild. Running the ScanNetworks example shows the networks in the area including the one that I am trying to connect to. I have tried to search the forum for solutions to this but haven't had any luck. What does the error LED mean? Anyone have any thoughts on getting this to work?
I figured it out!!! 
(finally!)
The mac address on the sticker that came with the wifi shield was wrong and I had my network set to only allow certain mac addresses. I removed the restrictions on the network, the shield connected and printed out its real mac address. Then changed the address in my network restrictions and re-enabled them. It works fine now 
can you say me, how you do it???
I had the same issue, if it helps anyone, my router broadcasted at 5Ghz and 2.4Ghz. Only 2.4Ghz would work for me!