SketchUp Pro: Problem with Materials Trays

Hello, I have a very slight problem with the Materials Tray (see attached image). I created a new siding material (the one with blue highlight around it) in the top tray. I cannot seem to drag n’ drop it into the lower tray (currently showing my brick, cladding & siding textures). When I drag the texture from the top tray, it will not appear in the lower tray. I watched a YouTube vid where the guy was able to do this, so I’m a bit perplexed as to why I can’t repeat his steps. Any suggestions?

(The attached image may appear collapsed here, please click on it to expand it to see both trays.)

Thanks-

Check out the reply by DaveR on another post about this issue.

http://forums.sketchup.com/t/cant-drag-a-material-from-one-material-palette-to-the-other/31009/1

Which was a reply to @Joel_Cairo with the same question.

Ah, yup. Dave is right. I did ask this question before. My bad. I would delete this thread, but I see no option to do so.