2006 Prius Shifting problem

I drive a 2006 Prius that up until now hasn't had any significant issues. Today, while backing up, I stopped completely and tried to shift from reverse into drive. I depressed the gas pedal slightly only to find that I was still in reverse. I also noticed a weird sound coming from the dashboard yesterday morning while stopped at a light. I can't really describe it except that it sounded like a washing machine (closer to the end of a cycle, when the clothes are sort of sloshing around). My close friend, who drives a (used) 2007 Prius has the same shifting problem, but her car does it almost every week whereas I think this is maybe the first time that it has happened to me. I was just wondering if this has happened to anyone else? It might be user error as I was in a rush, but it was really scary nonetheless.