Game froze / crashed

I was playing with a friend, we have a 348 day old server. All of a sudden we couldn't move, but could still use the inventory menu and use the crafting menu, but not be able to craft or move items. He then shut down the server (he was host), and could not see any animations in the main menu (the Florid Postern). He could still move the cursor and move throughout the different sub menus. He could still hear sound though.