Canon i255

While I'm not familiar with this unit, the common problem for a paper jam is a foreign object (small piece of paper, staple, paper clip...) caught in the paper feed path somewhere. Slick, worn rollers, a broken gear, or other problem in the drive mechanism will cause such as well. Rarer would be a circuitry problem (motor drive circuit for example).

Sorry I can't be more specific- but a careful look at the paper path is the first possibility.