I seem to be having an issue with Tinker's Construct. It crashes whenever I enter the smeltery's gui. I should probably mention that I'm also using Iguana Tweaks because I like the leveling system but I doubt that would cause any errors.
http://pastebin.com/iKpSTkTx
EDIT: I tried removing Iguana Tweaks but it didn't help so that's not the problem. It's something to do with TiCon itself.
First of all this is a rendering issue.
After checking the error log, I noticed that TC fluid registry's are broken.
This is a forge problem after version 1351/1352, due to the reason that forge changed how fluid registry's work, one option is that I could fix this issue, is by downgrading forge, however I will have to downgrade a lot of mods as well.
Another option is wait for a Tinkers Construct to update.
I'm pretty sure some TC updates would be coming soon to fix this issue.
May I ask what ore was in the smeltry?
Thank you for informing me about this bug, it really helps improving the modpack!