[ZPT] nesting fill-slot - used to work?

[alan runyan]

sorry, but I looked through the archives and couldnt find anything.
actually I found Geir asking about the same issue last year.
I'm running Zope2.5.1

in CMFExample found at sf.net/projects/collective I have a PageTemplate that
nests fill-slot.
use-macro="main_template/macros/master"
   fill-slot="body"
       fill-slot="main_columns"

now.  the crazy thing about this.. it *use to work* i.e. after the import of
the .zexp the PageTemplate isnt broken.
but if I try to edit anything then I get the error:
Compilation failed
TAL.TALDefs.METALError: fill-slot must be within a use-macro, at line 65,
column 1
but at one point this worked.  because I did it.  maybe I was using a bug
inside of PageTemplates that has been sealed?
any help appreciated.

~runyaga