On Fri, 2012-02-24 at 05:34 +0100, Wolfgang Schuster wrote:
> You should make a minimal example with \starttextbackground which produces the same error as your document.

As a minimal, it seems to work. But as part of my book, it bails with
the following:

graphics        > invalid region for 'tbg:1'
! LuaTeX error /usr/share/texmf/tex/context/base/anch-pgr.lua:530:
attempt to index field 'list' (a nil value)
stack traceback:
	/usr/share/texmf/tex/context/base/anch-pgr.lua:530: in function
'fetchmultipar'
	/usr/share/texmf/tex/context/base/anch-pgr.lua:569: in function
'fetchmultipar'
	<main ctx instance>:1: in main chunk.
\ctxcommand ...\directlua \zerocount {commands.#1}
                                                  
<argument> ...tipars {\MPvar {self}}{\MPanchorid }
                                                   ; \includeMPgraphic
{\MPv...
\meta_process_graphic ...graphicformat ", \!!bs #1
                                                  ;\!!es , \!!bs
\meta_flush...
\anch_positions_meta_graphic_use ...#3\stopMPcode 
                                                  \endgroup 
\anch_positions_meta_graphic_nested ...graphic #2}
                                                  \endgroup 
\anch_positions_meta_graphic_direct_indeed ...ame 

\removelastspace }\smashbo...
...
l.206


I am using it as such:
\starttextbackground[CodeExampleFrame]
...
\stoptextbackground

And the background is defined as such:
\definetextbackground[CodeExampleFrame]
   [corner=round,
    frame=on,
    before={
        \blank[2*big]
    },
    after={
        \blank[2*big]
    },
    color=color_text,
    background=color,
    backgroundcolor=colour_page,
    framecolor=colour_text,
    location=paragraph,
    topoffset=0.5cm,
    bottomoffset=0.5cm,
    leftoffset=0.5cm,
    rightoffset=0.5cm]

This is with ConTeXt version 2012.02.21 14:02 MKIV  fmt: 2012.2.26.

-- 
Kip Warner -- Software Engineer
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http://www.thevertigo.com