\setupinteraction[state=start]
\starttext
\reference[ref:UsersMan]{User's manual}
\input tufte\par
User's manual~\at[ref:UsersMan]
\stoptext

=========================================================================
> This is LuaTeX, Version beta-0.42.0-2009071712
>  \write18 enabled.
> (test.tex
>
> ConTeXt  ver: 2009.08.14 10:48 MKIV  fmt: 2009.8.14  int: english/english
>
> system          : cont-new loaded
> (C:/context/tex/texmf-context/tex/context/base/cont-new.tex
> systems         : beware: some patches loaded from cont-new.tex
> (C:/context/tex/texmf-context/tex/context/base/cont-new.mkiv))
> system          : cont-fil loaded
> (C:/context/tex/texmf-context/tex/context/base/cont-fil.tex
> loading         : ConTeXt File Synonyms
> )
> system          : cont-sys.rme loaded
> (C:/context/tex/texmf-context/tex/context/user/cont-sys.rme (C:/context/tex/texmf-context/tex/context/base/type-tmf.tex (C:/context/tex/texmf-context/tex/context/base/type-tmf.mkiv)) (C:/context/tex/texmf-context/tex/context/base/type-siz.tex (C:/context/tex/texmf-context/tex/context/base/type-siz.mkiv)) (C:/context/tex/texmf-context/tex/context/base/type-otf.tex (C:/context/tex/texmf-context/tex/context/base/type-otf.mkiv)))
> system          : test.top loaded
> (test.top)
> fonts           : preloading latin modern fonts
> bodyfont        : 12pt rm is loaded
> language        : language en is active
> systems         : begin file test at line 2
> (C:/context/tex/texmf-context/tex/context/sample/tufte.tex)
> fonts           : resetting map file list
> {C:/context/tex/texmf-context/fonts/map/pdftex/context/original-empty.map}
> fonts           : using map file: original-base
> {C:/context/tex/texmf-context/fonts/map/pdftex/context/original-base.map}
> fonts           : using map file: original-ams-base
> {C:/context/tex/texmf-context/fonts/map/pdftex/context/original-ams-base.map}
> fonts           : using map file: original-ams-euler
> {C:/context/tex/texmf-context/fonts/map/pdftex/context/original-ams-euler.map}
> fonts           : using map file: original-public-lm
> {C:/context/tex/texmf-context/fonts/map/pdftex/context/original-public-lm.map}
> fonts           : using map file: lm-math
> {C:/context/tex/texmf/fonts/map/dvips/lm/lm-math.map}
> fonts           : using map file: lm-rm
> {C:/context/tex/texmf/fonts/map/dvips/lm/lm-rm.map}
> ! LuaTeX error ...text/tex/texmf-context/tex/context/base/node-ref.lua:47: attempt to call upvalue 'list_dimensions' (a nil value)
> stack traceback:
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:47: in function 'dimensions'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:71: in function 'inject_range'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:302: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function 'inject_area'
>  ...text/tex/texmf-context/tex/context/base/node-ref.lua:299: in function <...text/tex/texmf-context/tex/context/base/node-ref.lua:279>
>  (tail call): ?
>  <local nodes_cleanup_page = nodes.cleanup_page...>:14: in function <<local nodes_cleanup_page = nodes.cleanup_page...>:10>
>  (tail call): ?
>  (tail call): ?
>  <main ctx instance>:1: in main chunk.
> \finalizeshipoutbox ..._page(tex.box[\number #1])}
>
> \actualshipout ...0\hbox {#1}\finalizeshipoutbox 0
>                                                   \setbox \scratchbox \hbox ...
> \myshipout ...\@@ppmethod }\gobbleoneargument {#1}
>                                                   \setnextrealpageno \afters...
> \dofinaloutput ...hbox {\vbox {\dopagebody #1#2}}}
>                                                   \the \everyaftershipout \a...
> \finaloutput ...EAEAEA \dofinaloutput \fi \fi #1#2
>                                                   \resetselectiepagina \incr...
> \sidefloatoutput ...e \else \finalsidefloatoutput
>                                                   \global \sidefloatvsize \n...
> ...
> l.6 \stoptext
>
> ?
=========================================================================

Thanks,
Tad

PS: By the way, the LuaTeX version being distributed in the latest Windows minimals is back to 40.6.