Of course it's easy to break something if you change something you haven't touched in awhile and don't remember how it works, but to my knowledge, nothing has changed about the furnaces, the fuels that go into them or the items that can be made with it, aside from the new chicken and beef items. Even then, adding new items to a list of items cookable with the furnace doesn't break it.
For what it's worth, it is the lighting system that's fucking with my client. Placing a torch, starting up a furnace or having the sun start to set just flat out crashes me out, so I'm betting it's graphics card related problems. 1.8 will be unplayable for me until someone makes a mod to remake the old light system unless Notch or Jeb implements some changes are made to it *over the weekend on personal time* (hint: not gonna happen).
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╕..Х 'ии)) -:ж:-
╕.Х' .Х'ии)) Katelynn -:ж:-
((╕╕.Х' д ║░ д -:ж:- |
(п`Х.Х┤п) (п`Х.Х┤п)
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д ║░ д`Х.╕.Х┤ д ║░ д |
Lewis: Ok, we need to gain the trust of some villagers.
TotalBiscuit: I think Simon's qualified to do that!
*Simon approaches a villager and summons a swarm of angry bees*
Simon: Hello! Do you like bees!?
*The villager drops dead from the bees*
Simon: Oh dear... Um, that could have gone better...