Network IP problem

I have a Netgear DG834G network which works fine on wireless & cable. However in one room the wireless has a poor or non existent signal so I have installed a Linksys Powerline AV Ethernet Adapter. Whichever computer I try to get on the network with (all are running on Windows XP professional) using the adapter on either wireless or cable finds the network but the network will not allocate an IP address to allow connection to the internet. Any ideas?