[member="mdlogan"]
What I can say is that long ago, a player by the name of Akio had the same issue. My only advice, as initially successful that time, is to simply use a different browser such as Chrome - whatever browser he or she is not on. I'd also advise clearing out your cache and all of that (not your cookies though, that won't do this).
I use both Chrome on my laptop and Firefox on my desktop and can not only browse both simultaneously but use two subaccounts from the same main at the same time with absolutely zero interference. Whatever this is, it's an isolated issue. If you have any more details, such as ISP, router type, actions prior to issue, etc, I might have more insight for you comparing to the other times I've heard this happen.