Can't connect to AE with my PC (Windows XP)

Question

I've been connecting my PC (Lenovo Thinkpad, Windows XP SP 3) and my eMac to my Airport Extreme for over a year, but my PC suddenly stopped being able to connect.
The AirPort Utility on my PC doesn't see any base stations. My PC's wireless utility, Access Connections, sees my network, but fails to connect to it.
When Access Connections fails to connect it asks if I want to configure the network and there's a bunch of settings. Connection type: infrastructure or Adhoc, Wireless security type "use static WEP keys", "Use Wi-Fi protected Access - Pre Shared Key (WPA-PSK)" - I choose it and under Properties there's more options. Access point authentication, WPA-PSK or WPA2-PSK; I've tried it both ways. Data encryption: TKIP or AES, I've been using TKIP. Under Pre-Shared Key, there's the only box I see to enter a password, so I enter the password there.
I tried reconfiguring the AirPort using the AirPort Utility on the eMac, changing the name and password. Didn't help.
I've been connecting my PC to the AirPort Extreme through an ethernet cable and it works fine. I even ran Airport Utility on my PC and it saw the network. I saved it. But when the ethernet cable's unplugged the same problems persist.

Answer 1

When Access Connections fails to connect it asks if I want to configure the network and there's a bunch of settings. Connection type: infrastructure or Adhoc, Wireless security type "use static WEP keys", "Use Wi-Fi protected Access - Pre Shared Key (WPA-PSK)" - I choose it and under Properties there's more options. Access point authentication, WPA-PSK or WPA2-PSK; I've tried it both ways. Data encryption: TKIP or AES, I've been using TKIP. Under Pre-Shared Key, there's the only box I see to enter a password, so I enter the password there.
Chances are pretty good that the problem is the network configuration of your PC and not the AirPort Extreme Base Station (AEBS). What configuration options you choose will depend on how you set up the AEBS's wireless network, but the following can be used as a guideline:
o Connection Type: Infrastructure
o Wireless Security Type:
AirPort Setting = PC Setting
o WEP = WEP
o WPA Personal = WPA-PSK w/TKIP
o WPA2 Personal = WPA-PSK w/AES