I just upgraded from Photoshop 7 to CS3. They seem to have changed the behavior of effects and styles on layers.
It used to be if I dragged a single effect from one layer to another, it would COPY it to the 2nd layer - requiring you to remove it from the original layer if you were intending to MOVE it from one layer to another.
In CS3, it seems dragging single effects automatically MOVES it. Although you can choose 'Copy Layer Style' and 'Paste Layer Style' off the layer menu, I often just want to clone a single effect with all its settings to another layer.