Please post what browser you are using, when you're discussing this. I spent a lot of time today trying to debug this, and haven't been able to come up with anything. It works on every browser on my system.

Okay I've just added a new icon (that looks like a move icon) that you can use to layer the items, drag from there, until I'm able to resolve the problem with the images in firefox.

does the new dragging thing not work for you?