Jack,
Part of the reason is that the standards weren't originally created tightly enough. This leads to interpretation, which leads to incompatibility between vendors. This has certainly affected security standards WEP (sorry, I think I said WAP in my previous post) and WPA, however WPA2 seems to be a bit more resilient as standards go.
Discussions with a friend at Netgear point to the wifi consortium centralising around easier settings, which include WPA2/PSK/AES (PSK = Pre-Shared Key).
I would suggest you go tinker with your wifi access point, call it a different SSID (because Windows remembers the settings of previous SSIDs unless you get it to specifically forget them), choose channel 6, with 802.11g/n and set it to WPA2/PSK/AES, and see how you get on with connecting. It doesn't theoretically matter so much that you understand the wifi technology, but setting to those settings should help overcome most eventualities.
Cheers,
Mike.