OS 10.5 - Network shared spaces verrrrry twitchy

I've been having some issues with accessing other computers on my home network. It used to be that sometimes the other computers wouldn't show up under the "Shared" list in my finder window, and if I restarted my macbook they would show up, but recently, they stopped showing up entirely.

I'm not even sure where to begin with this. I've looked through the hetwork settings on my macbook but nothing seems to fix my problem.