I believe it is hardware not outside influence, ISP, power or anything like that. With all the games going down, they could have just bombed the Controller that runs the VM farm the login servers run on. That would suck. No loss of data, but if the hardware issue is bad enough could take them a while to resolve.
Old gaming server joke from way back. Server go down unexpectantly and it is always 'cause a dead hamster that was ran to death on his wheel to power the server.