If it's any consolation to anyone, this exact same issue has been happening to me for the past 3 days. I don't think it's a browser issue (I've used Firefox, IE, Safari, Opera); it's not a PC issue (I've tried different computers); It's not an IP issue (Staff in other countries experience the same).
I run on a Centos5 VPS. I reboot, I power-cycle, hosting support help me, no luck!
Eventually, last night I bought a new VPS and this time chose UBUNTU. So far, no problem.
I'm now in the process of setting up everything again.