Can't log on to my Yahoo account.

I work on an oil rig overseas. The rig has two networks, one for all of the work computers, and one for everyone else. I am using the one for everyone else of-cores. When I first starting using the this network I had no issues. But now for some reason when I try to log into Yahoo it gives me (Safari can’t open the page “https://login.yahoo.com/config/login_verify2?.intl=us&.src=ym” because Safari can’t connect to the server “login.yahoo.com”.) I even installed google chrome, and tried it from there with no luck. I can log in useing any other computer on the rig, so I don't think it's the network. Can some one help?
Thanks

Just got off the phone with Apple support. He could not fix this issue at this time due to I had to get off of the phone due to duties at work. But we did find out it is just login pages I am having issues with. Not only yahoo, but I can't log into Facebook, or youtube ether. But I can watch videos on youtube.

Have you tried creating a new account and password?

If you are referring to a new Yahoo account, I can't even bring up the log in screen. When I try any of the accounts mentioned above I get the can't open page when it tries to get to the login page. Crazy I know....

Well the issue is finally fixed. What needed to be done, was every thing from web proxy (HTTP) to Gopher proxy needed to be checked, and the same address, and port put in.
Thanks to all the guys @ Apple support for working so hard on this issue. They were really good to work with, but they did not find the problem. The Driller, on my rig I work on did. But I still think Apple support did a good job trying.