Playing SSP in 1.8.3, I have often found that my snow golems and dogs become invisible, but can still be heard. This also sometimes affects my cows and maps in item frames. This is always resolved by exiting and opening the world, and occasionally resolves itself if I leave the area and come back. Nothing has become invisible while looking at it, only while I was away. No potions were used, and the dogs' collars did not show, so armor layers were affected as well.