I'm having a similar issue, though simpler perhaps. I can no longer drag a layer from an open PSD document into another open PSD document.
I click on the active layer, then drag it to another tab at the top - previously the other open document would become active, now it just shows the circle with the line through it and remains on the document the layer came from. When I let go of the mouse button, the layer is unchanged.
This worked just the other day; not sure what changed. I closed the program and restarted it with no change.
Windows OS 8