Debian 6.0.6 with 2.6.32-5
Click, drag, drop, is unresponsive
Make use of Firefox Addons to Sort/Organize your Bookmark
I guess the Library should sort. I use Ubuntu rather than Debian but on both Ubuntu/Canonical and Mozilla Firefox versions the bookmarks within the library do drag and drop etc.
I suggest that first of all you back up your bookmarks, and also make a copy of the database file places.sqlite then see if anything can be done to address the problem