Alrighty so I'm using a Sierra Wireless AT&T card on my mac and I'm wanting to share the connection from my mac ( Late 2008 new macbook running OS X 10.5.6 ) over airport to my brother's Dell using Windows Vista. I went into system preferences and turned on internet sharing via airport and set up a WEP encryption with a password. So I started broadcasting the connection and both mine and my girlfriend's iPhones pick up the signal and can access the internet. Oh, and so can my brother's iPod touch. The problem occurs when I try to connect to the network from my brother's laptop running Vista. His computer sees the network but when I try to connect, it fails and gives me a "diagnose the problem" box. When I click that it says something to the extent of "the wireless network security settings for this computer don't meet the requirements of this network." It also says "click here" to view said settings but when I click it just closes the dialogue box. I've tried both the 40 and 128 bit encryption WEP settings but to no avail. Does anyone have any idea what settings I need to modify either on the Dell or my Mac?