I had a similar problem recently when fixing a friend's laptop. My router (BT Home Hub) puts out a signal that I've never had a problem connecting to from anywhere in the house. This has been done with several laptops and the Netbook that I'm using just now, but this friend's laptop wouldn't connect unless I went into the room with the router (and close to it as well!). This was weird, I then looked at the configuration settings for his wireless card and found that there was an option to optimise for distance. I changed to this and it then worked like all others.