[Bug...?] Login Troubles

On occasion, I'm automatically logged out of the NA boards (I assume this is due to timeout). However, upon logging in again I'm told that my password is incorrect.

I'm directly copy/pasting from LastPass and matching the CAPTCHA, so I know this isn't the case. Additionally, this only happens sometimes and I'm unable to recreate it systematically. Other times I can log back in without issue.

Any ideas as to why this may be happening?

EDIT: I think I replicated a way to resolve this.

Upon the issue happening again, I visited the primary site (leagueoflegends.com), clicked my profile, and then went to the boards. With great happiness I found myself to be logged in. No idea why this would fix the problem.