The game wont connect to any servers or single player worlds. it is crashing every time i try to get into one. it also keeps glitching.

when i go into the multiplayer none of them will connect. when i try to load a world it crashes. and sometime it glitches while playing. or it did when it let me in.

What I expected to happen was...:
i though it was all fine and dandy but then it crashes

What actually happened was...:
all i did was try to get into a survival world and it crashed while loading

Steps to Reproduce:
1.log into minecraft
2.go to singleplayer
3.pick a world or create a new world to play on
4. when its loading terrain it crashes