The only time I can get it to happen is by pressing Shift+Enter after inputting my username/password.
hmm that could be it, that makes it happen for me too. i tried seeing how it felt to "accidentally" press shift with enter, and i don't think that's what i've been doing...my keys aren't close together like a laptop keyboard, so it feels pretty noticeable when i press 2 at once, i'd like to believe i would have noticed that mistake. i'll try to see if it ever happens when i can confirm i definitely didn't press shift now that i'm aware of that.