Well, I just tested it and it looks good to me !!!
The animations are playing well and the model doesn't change it's size !!!
I tested it in tutorial #1 with DX and OpenGL...
Try it with tutorial #1 and look if the error is there, too !!!
And maybe try to export the model to an other format, like DX or 3DS !!!
If it works with tutorial #1, then something must be wrong with your code...
You also can post your code here...