Don't know if this has been mentioned, if so sry but here goes.
I was playing earlier and after loggin in fine from the initial little box that first appears with the news etc etc. I went afk for a while and was automaticallt logged out. With the game still running and on a log in screen I tried logging back in. But my username and password were reject.
After existing the game and launching everything worked fine again. For some reason logging in through the game log in screen wouldn't work. A bug? I thing so.