So, in 1.2.5, Mojang added shift clicking support in furnaces. However, every time I try to shift clock something in that isn't smeltable, my minecraft immediately freezes and blackscreens. I would be testing this independently but tomorrow I leave for 3 weeks, so I'm asking you. If you're bored, get a furnace and play around with the shift-clicking. If you find a recurring pattern with crashing, please put it here and I'll check it out when I get back. Or, if nothing wrong happens, let me know so I can tell if it's just me or not.