Just something dumb, but something like this happened to me awhile ago. I began having issues with all of the passwords to all of my internet accounts.
As it turned out I had a letter on my key board that was intermittently failling to work. when typing normally, like when writing a message or letter ect, I would see that the letter was missing and just type it in without thinking about it. but when typing out a password I couldn't see it was missing so all of my accounts were refusing to let me in.
just out of a simple check and see mentality, try a different keyboard. if everything works then you probably have your answer.
If it doesn't, well I did warn you at the beginning "Just something dumb"
Good luck
FLOTSOM
