i think you are saying that you can't apply a mask to your image?
there are bugs in Qt that juan worked pretty hard to overcome, and one side effect is that the drag/drop of process icons and masks has become a little bit difficult. if you are slow and careful, you'll find that you can drag a mask onto another image. the problem is that if during the drag, the bug is triggered, then no matter where you release the mouse, you get a clone. it sounds to me from your description that this is what is happening.
if push comes to shove you can always right (or control-) click an image to bring up the contextual menu and Mask > Select Mask (or clover-M) and pick the name of the mask from the dropdown list.
rob