Need help on skeletal Animation

Hello, I'm a young student making a video game with some of my colleagues. We've been trying to figure out a quick and efficient solution to do animations. We know sprite sheet with unity 4.3 can work, but we think that using skeletal animations will be a lot more quicker.

So I just download Unity Sprites and Bones, a free package that allows bone creation in Unity itself, and is for free. However, I have a huge problem with this software,every time a make an animation with the bones, every single time I run the animation, some of the bones flip out and twist in weird directions.

So my question is, is there any way to fix this problem? Or should I just call it quits and use Sprite sheet animation? Also, could you point to me actually working and useful animation tools that might be better than Unity Sprites and Bones?

Link to Unity Sprites and Bones: http://forum.unity3d.com/threads/219915-Release-Free-Unity-Sprites-And-Bones-2D-skeleton-animation