Thank you for your post.
I was able to replicate the problem. I have forwarded your post along with my findings (also Mac OS X 10.5.x and 10.6.1), to our Development and Software Quality Assurance (Testing) departments for review and confirmation. As more information becomes available, I will post here.
Until this is changed, you may want to consider keeping a dummy file active in the sub-folder so it is always accessible.