I have a Netgear DG834PN and it's playing up on me.

There are four computers in the house, one is connected using ethernet to the router and the others connect  using wireless. But one of the computers won't connect to it.
It's running Windows Server 2003 and using a Netgear WPN111 adaptor, it picks up the neighbours wireless networks (although they're both secured, so I can't use them) but won't pick up my router which is a few rooms away. It's not out of range because a different computer using the same adaptor can connect in the same room.

I'm stumped, any ideas?