linksys connection problem

I'm trying to help my friend with his internet problem. His wireless internet connection is acting weird. The icon says he's connected, but everything's screwy. Aim doesn't work right, he can't load pages etc. Google will usually come up and he can do a search, but if he clicks on any search links nothing really happens (99.99% of the time nothing loads). When I go to 192.168.1.1 I get the password prompt, but nothing happens when I enter the password. And there are other computers in the house with wireless connections that are working fine.

I thought it was a problem with his computer, but when I took his laptop to my house to scan it, the internet worked perfectly. And I could access 192.168.1.1 at my house. So...I don't really get it. Can anyone help me out here?

I don't know if this is necessary, but:
router: BEFW11S4 V.4 802.11B
adapter: LAN-Express IEEE 802.11 PCI Adapter
and he's using XP

 

Signal Strength?

 

I don't think that's the problem. It doesn't matter whether he's in another room or right next to the router--he still has the same problems.