Ive seen a case like this as well in the case of someone who has installed Railcraft.. It looks like there was recently a new block type installed for systems running a updated version of Railcraft "Hidden Block".. And Originally on one of my custom builds i had a case where the Smeltery Refused to fire up.. The solution is to go into the railcraft config file.. and change "Hidden Block" to "0". Then after i restarted that fired up without a problem.. However..your most likely culprit is either its not built properly or something like railcraft is conflicted with it. (Note.. on the Railcraft Fix.. I claim no responsibility of anything that comes of altering that file.. Its something I had googled and found on the Tinkerers construct Mod Forum that resolved the issue for me.. Milage may very)