Broken?!?

Amm, ok so i was on a server just before and when i exited and re-opened the multiplayer interface to enter all my servers were gone!! Then i went in one of my worlds and well, first i summoned a villager (I was creationg a map) and he was invisible but still there i could here villager voises but not see him so i killed him then got out of the structure and sudently all mobs were invisible and large things were showing on there!! I entered an other world to see if it had affected that too but it was also the same thing all broken.... PLEASE HELP