The player and all mobs are invisible. You can see the shadows beneath them, hear the sounds they make, and interact with them, except that you cannot actually see them. Additionally, I uninstalled and reinstalled minecraft, along with deleting all of the contents of the appdata folder for minecraft. Not sure what the problem could be here.

Attached is an example of two invisible mobs upon the creation of a new world, along with an example in third person mode of the player holding a block of dirt. It seems that only mobs are invisible, along with some specific items like chests (a chest in another world was invisible as well, which doesn't seem to fit with the pattern).