My last paycheck was withheld. The company said that the Pay Period dates listed on my paycheck were wrong. They proceeded to make up a "correct" pay period date, which made it so it looked like I already got paid for that Pay Period.

Very deceptive business practices and bad accounting procedures. Employees should be notified of this practice and be very careful about checking their paychecks. The ethical thing for the company to do would be to admit their mistake and make restitution IMMEDIATELY to all those employees they did this to.