Dude, I think what Rumsponge was meaning is, have you tried logging in from a different system, other than the one you regularly play from? It could actually be a problem with your account on your computer. It sounds strange I know, and it actually is. But there is a possability that there is something, maybe a hidden file or whatever in cache or elsewhere, that is not getting properly cleared. When you sisters account logs in it does not show as it is something associated with your account, thus it only effects you. So if you can try to log in from another machine, please try that and report the outcome. If you still have the problem, capture the logs and screenshots for support, as it a problem with your account and you have something to show that. And request a different support person if you can.
That is about the only thing that makes sense to me. Hopefully maybe just a little it might help. If it does not, sorry it's the best I can come up with at this moment.
KD