You are placing it where you had the iron furnace previously.
From what I've heard it's a forge bug, but a work around is to pick up all affected items, restart MC, then place them again and they will work correctly. Until the next time you pick them up, and try to put something else in it's place.
Apparently, there is an issue with blocks updating. Basically if you have to remove any IC2 Stuff (including wiring), remove them > quit > restart > place items where you want them.
It is affecting all types of blocks too, if you place a dirt block where a generator used to be, you can use a wrench on the dirt block to remove it 
From my limited knowledge of how IC2 and Forge work, my guess is that the tile entities aren't updating right. Please tell me someone has a fix going into Forge soon.
I figured it was probably something Forge-related. I'll try the pick up/restart thing. Thanks.
It is. Try forge 57. Shouldn't happen again.
