Organising images

I am using version 1.5.1.3. I have set up some sub folders in image manager with a view to organising my images by category. However, I don't seem to be able to move any of them from the top folder in to a sub-folder. When I select an image and click on "move" I appear to get a drop-down box with a submit button next to it, but clicking on the down arrow doesn't do anything. Is this a bug or is it me?
I can upload directly to a sub-folder but not move anything from the top folder to a sub folder.
Any ideas?
Thanks.
Chris.

Interesting that I have found that the "move" function works fine in Chrome but not in IE8.