Pacman Syndrome derives from the arcade game, Pacman, and is used to describe the issues with the opposite sex when in a relationship or single, in the terms of Pacman.
In a situation where Pacman Syndrome is present the opposite sex is described as the "ghosts", and the individual as "Pacman".
Those in a relationship:
In the arcade game Pacman is chased by the ghosts, and tries to stay away from them. This represents that the individual is pursued by the opposite sex while in a relationship, and attempts to keep away, in order to avoid being unfaithful.
Once Pacman eats a power-pellet (representative of a break-up), he can then pursue the ghosts. This represents that after a break-up, the individual then switches, and begins to pursue the opposite sex, who in turn, try to keep away from the individual.
"Dude you have the worst lock with girls."
"I know... its Pacman Syndrome."