I recently connected a Buffalo WHR-G54S to an existing wired network to act as a wireless access point. Right now I am connected to the internet via the WAP, but I cannot connect to the access point web based control panel. I am using the supplied IP address that was in the manual. Hoepfully you guys can help me out.

If the AP was setup properly it should have a static ip so it can be accessed on your network. If not, look at your routers DHCP log and find out what IP it is set at. You may need to do a direct connect to the AP with a wired connection to access it. If Not reset to factory and follow your setup guide.