adoptNode fails if node type element has collapsed attribute?

seems odd but here is the scenario: in TotalToolbar i reuse some 
customize code to move statusbar items around.  the process is to first 
cloneNode each <paletteitem> and apendChild to the statubar's palette; 
for an item that is dragged to the palette first a cloneNode from the 
palette is done then a document.adoptNode and finally an appendChild to 
a wrapper that is inserted/added to the Customize window row element etc.

(this is how toolbar customization is done, for better or worse).

a particular button (download statusbar) has a collapsed=true 
attribute.  removing this from the extension's xul (must remove, cannot 
set to false) eliminates the adoptNode failure.  testing with 20+ other 
statusbar buttons works fine.  bug?