I’ve been spending some time trying to get a Laptop running Windows Vista connected to a wireless network where the SSID is not being broadcast. I tried all kinds of different security settings but nothing was working. I then stumbled across the solution in this article:

Non-broadcast Wireless Networks with Microsoft Windows

When configuring the network ensure that the ‘Connect even if the network is not broadcasting’ option is checked. Can’t believe that I never thought of trying that – seems so obvious in hindsight!