Do you happen to know anyone who holds a particular grudge against you?
Like, anyone you've recently quarreled with or anything?
If not, there is a small chance that you've been hacked and you've probably just got the password wrong.
Maybe you accidentally pressed alt-shift and changed the keyboard settings to make them type another language, or just used num/caps lock.
If you are 100% positive that you've typed the password right, and somebody does hold a grudge at you, there is a possibility of a hacker, even though unlikely.
Do you have any IRL friends that saw you type the password at home?
Since the password is not blurred out it is possible that they remembered it.
Edit: Cutter beat me to it, I guess you just mistyped your password.