Okay, just tested these on a fresh MultiMC instance using MC v1.5.2, MC Forge v7.8.0.689, IC2 1.115.308-lf, and the currently available versions of your mods. Here are the results.
Flat Signs: Wouldn't even let MC fully startup.
http://pastebin.com/HiP7EN3J
Obsidian Plates: When I click on...