When I'm using a GUI (eg. Enchant, Crafting, Furnace, etc.), the world in background stop to render and all gets like when you are flying high: without any blocks visible. Sometimes, the world in background "flashes", appearing and disappearing. Another thing I related is that only the water is rendered, and all other blocks disappear. And sometimes, nothing happens, and all is normal.
Testing it one more time, I related that sometimes it can happens when I'm with an enchanted item in the mouse pointer. When the item is not enchanted this not happens, but the GUI name letters get white. When I pass the item from hotbar to inventory, it becomes white. When I pass from inventory to hotbar, it becomes black again. And when I PLACE the item in a INVENTORY slot, it becames gray.
Another thing that also happens: when I put the mouse pointer on an item that not enchanted, the world appear. When I take the mouse pointer, the world disappear again.