Game keeps freezing/crashing (Ipod Touch 4)

Ever since I have updated to Verison 9 of Pocket Edition, my game keeps crashing every time I play it and it is also extremely slow. Sometimes I can play for awhile where other times it crashes almost as soon as I spawn into a world. My sisters have new Ipods with IOS 7 and theirs seem to be working, so I'm not really sure what is going on but I love the new update and really would love to be able to play it!