Solution: I was not running my animations from a localscript within the character.
I've created a quick rig to demonstrate my error. My apologizes that the code isn't very clean, I wrote it quickly.
It doesn't seem to be a syntax error, as my animation plays fine on the dummy. When I try to play it on the character, it won't seem to work. It may have something to do with the humanoidRootPart being welded to the torso... but I'm not sure.
There isn't any code to really paste, as it's mostly straight from the wiki. The code works on the dummy, not on the character.
http://www.roblox.com/Custom-Rig-Errors-place?id=214493311
Please take a look and give me any ideas you have. Beginning to get a bit desperate, thank you.
I've had that same problem before.
Just unanchor your HumanoidRootPart. If that doesn't work, check back with me. We'll sort something out.