Model scale/perspective issue

I’ve been working on a model and I’ve ran into a problem that screws up the scale/perspective of the models arm. Oddly enough it only happens once a certain bone has been moved.

As you can see the left arm is completely fine so far.

But as soon as I move the upper arm this happens.

I’ve already tried reseting xforms which was an earlier suggestion on fixing it but that only screwed up the model more. Does anyone know how to fix this?

check your weights? otherwise try moving the arm in another modeling program. or even in source. Milkshape had a problem of blowing up verticies on the end of a bone like a balloon. it was just how milkshape thought it would look like, it looked fine in game.