Windows 7, Blender 2.78a
When you have a lot of textures on one object, the dropdown list bugs out, showing the headers below its child items and the scrollwheel direction is reversed.
Steps to reproduce:
- Startup scene, select cycles renderer, select the default cube, go to materials and set to "use nodes"
- Go to node editor, add a texture (for example checker texture, doesn't need to be connected to anything)
- In the properties panel, click the textures tab and verify everything is in place.
- Duplicate the texture 20 times
- The texture dropdown menu shows the described behavior
The behavior may depend on where the properties panel actually is and/or what the window position is. This was tested using the default layout.
It seems to me this is a quite obvious bug, if it has been reported already I am sorry for the inconvenience.