90001/90002 Errors...

First off, I'm wondering what does 90001 even mean. I know 90002 is when you have an issue on your end with the net but the 90001 has been appearing more frequently.

Now we recently changed our ISP from Bell Canada to Rogers Canada. We didn't have this issue crop up till then, but after being in contact with Rogers I was told it doesn't appear to be an issue on their part.

The 90001 also only appears when both myself and my sister have our desktop computers on. She and I both have accounts and when one of us is not connected, the other seems to be able to play just fine... I'm very confused, any help would be appreciated.