Saints row 2 doesnt work?

well whenever i play it starts out OK an i can still play, but as i keep playing i see less and less pedestrians and then there are none at first i thought it was cool cause no one to bug me or mess up my driving but then i tried to do missions and it wouldn't let me go into buildings i needed to go in and wont let me battle other gangs in missions either is it a glitch or wat cause i jus want to play i bought it NEW and had it 3 weeks never dropped it once