problem loading yahoo and other sites

[excalibur313]

I noticed recently that in both safari and firefox I am unable to open certain sites that work on other computers. It immediately states that it cannot connect to the server. Examples are yahoo, youtube, and a forum on college confidential.com. I tried resetting safari, clearing the cache, and repairing the permissions but none of that seems to work. What would be the next step to trying to diagnose this issue?

 

[emptyCup]

I do not have a problem with any of these sites. How are you connected to the internet? Is it the same way that the other computers you mention are connected?

 

[excalibur313]

We are all connected the same way, through a college ethernet.
EDIT: For what it is worth when running win xp through vmware fusion, I get the same error. My firewall is off. For what it is worth, I noticed this happening after a friend installed peer guardian on my computer. I don't have it running and I have restarted the computer multiple times but it still gives me this problem.