I am one of the many people who have been getting punted extremely often when zoning with an Unknown Error, only then to face an almost impenetrable wall of 301 and 315 errors at the log-in screen; and if I do manage to thread my way through that to the character select screen, it is likely I will again be booted with unknown error at attempted character entry to the world.
I have found when this happens, if I Restart my computer, I can get back into the game without any of the 301 and 315 errors, and can usually zone safely several times before getting kicked again.
I have only tried this a handful of times , but it is such an annoying problem I thought I would post this for others to try instead of testing it out more. It's not a great solution, but less annoying than the problem is.