Infamous glitching two times in a row?

so I really like the game InFAMOUS, which i got for free fro the PSN welcome back deal. However, I am on the level in which you have to destroy the Toxic Balloons, but, every time i get close to starting to destroy the final balloon, the game freezes. The sound continues but my controller does nothing, and the screen is frozen. I can't go to the PS3 background, or go to the menu. Help?????