What browser are the two of you using? I'm using Firefox, and it works fine. If the trouble's not your browser, try rebooting your modems (I know, I know--simplistic advice. But, sometimes it works.) A the very least, try contacting your ISP and your DSL/cable/whatever provider. Sometimes, they randomly block sites that they think get too much traffic.
I had the same trouble you're having, and I know how frustrating it can be.