Wireless Connection Issue

Hey all, I looked for similar threads, but couldn't find any, so hopefully someone has an idea here about this.

At my buddy's house, he has a wireless network set up with which all their PC laptops can connect. On my work computer (Macbook Pro), I see full wireless signal, but almost all the time trying to do anything online returns that I'm not connected to the internet. Once or twice it has worked, but the vast majority of the time, despite having a number of bars, I can't get anything to load.

The network has a password, which I entered originally and it seems to have accepted it. One of the roommates also has a MacBook Pro for work, and he sees the same thing.

Any ideas? Is there some setting within the router we'd have to change?

Thanks much!