It happened multiple times. Definitely had to be a hardware issue. SMB 3 was an all-day affair because I'd feel the need to 100% it. I'd play for a couple hours, eat lunch, play a couple hours, take a quick break, etc. I know I never beat it...It would typically freeze in worlds 6/7, but that was easily 5+ hours. God bless Super Mario All-Stars for save states...