I'm running AOBT 1.0.12a with 2GB available for the launcher on a MacBook Pro 2.7GHz i7 with 16GB RAM, NVIDIA GeForce GT 650M 1024 MB, OS X 10.9.4
The only config I have changed is to fix the ~ (tilde) bug for the morphs mod favorites key, set it to G.
As you can see in the screen shots below I am using the Chisel Mod chisel. Iron blocks will only give me the option of the normal Minecraft Iron Block. I've tried to use Chisel on many other blocks without any issues including the gold, diamond, and obsidian examples below.
Iron Block - http://imgur.com/OAMzxvK
Gold Block - http://imgur.com/ic7dG7c
Diamond Block - http://imgur.com/Bdz2iQN
Obsidian Block - http://imgur.com/Bdz2iQN
The chiseled iron blocks are perfectly accessible in creative mode but still not chisel-able:
http://imgur.com/vOThtas
Any help would be greatly appreciated.