I've had this problem since I first downloaded FML. I got it to run the mo creatures mod, along with Gui-Api and the Custom Spawner. The whole thing worked great, until I went to creative mode. When I go back into survival, I can no longer use my bare hands to mine anything. I have to use the tools. This even counts on leaves, dirt, and grass. Minecraft hasn't crashed at all, so I've never had an error report to look at.
I tried running minecraft without any mods, just FML, and it still does the same thing. Then I switched to Divine RPG, and it got worse because you needed to have a specific type of tool to mine anything. This is a real bummer on my game play. If anyone has any clue on how to fix this, or what I did wrong, that would be greatly appreciated.