I apologize for repeating a question but I was unsure if my previous post about this problem was placed in the right forum

This really makes no sense to me. My secondary computer is ether netted to this machine but when I attempt to go online (regardless of what browser I use; IE or Firefox[i] get a message that says(Firefox) "can't establish a connection to the server at my.earthlink.net" or with IE "Internet Explorer cannot display the webpage.
But I am able to sucessfully ping both yahoo and google with these results: four packets sent four packets received and 0 packets lost.
I called the ISP who is baffled as am I since the computer is online. What would produce this kind of problem and how can I resolve it? The IP (penteladata,ptd) gave up.
I don't know if this is the proper forum to use but I am in a quandry.
The problem computer was working fine 48 hours ago but now is simply unable to establish a connection even though it tells me the both the LAN and the Internet connection are connected. Please help me and ptd?
Thanks in advance