Apologies for the issues you're having. When we upgraded the server, the DNS (IP address) changed. A DNS change means the new IP must propagate throughout the internet across all proxy servers, hubs, and host-providers. This can take up to 72 hrs.
There's absolutely nothing I can do about this, as I have no control over it whatsoever. The only thing I can recommend is either the above solution - which may or may not work - or just wait until the DNS change occurs naturally. Depending on your ISP (or work proxy server), this can take awhile.
I could have posted the above information on the homepage, but again, it may or may not work, and would have generated even more e-mails asking for assistance for something that is way beyond our control.