iPAQ rx3715 WiFi shared authentication problem

[njl2016]

For about 2 weeks I've been able to access my wireless network with WEP-128 and shared authentication (on my Linksys router Wireless>Advanced Wireless Settings>Authentication Type: Shared (Default: Auto)) A few days ago, my iPAQ would only stay connected for a few minutes at most, then I would have to reconnect it. I turned off WEP and Shared key authentication and it worked. Then I turned on WEP with the authentication setting to Auto and it works fine. But when I change it to Shared it dosen't work. I read the help and it says that Auto allows open or shared authentication. So when I have to input a WEP key to connect that means it is shared authentication, right? How come when I change it to Shared (I also do this in the settings on my iPAQ too) it acts all wierd? Why this sudden change?