I'm new to this game, just played 1 week but already noticed how frequently this bug happens. And even when i tried to log off and on again, i still can't jump. However, when i opened the chatbox and try to type something in, the SHIFT button didn't work so i must assumed it has been stucking the whole time. Tried to use the SHIFT button outside of the game and it works fine. So i opened the game and tried to press SHIFT consecutively and it seemed to solve the problem.
Like the topic above, it DOES involve the "toggle sprint" option. I'll try to turn it off, for now, until i notice any significant changes.