select the hand and check for translate dials. If they show then ik is on.  Forearms dont actually move side to side so I would suspect limits.  I would look at the cr2 that doesnt work when loaded and see whats shown for that rotate parameter.

 

        rotateZ zrot
            {
            name Side-Side
            initValue 0
            hidden 0
            forceLimits 0
            min 0
            max 0
            trackingScale 1
            keys
                {
                static  0
                k  0  0
                }
            interpStyleLocked 0
            }

 

This is from V4.2 forcelimits 0 means no limits are in effect.

You can alter the limits for the parameter in poser.