Problem moving selected rectangle area

[pstein]

I am confused. After a while of not using Gimp I need to do something which worked the past worked...somehow.

1. I dragged a new image to Gimp
2. I selected "Rectangle Select Tool" and selected an area in the currently visible image
3. I selected the "Move Tool"
4. I clicked into the rectangle area and dragged it.

Surprisingly not the rectangle area is moved but the underlying whole picture.
Whats wrong?
How can I move selected are only?