[luatex] Plain TeX is not working

[Yue Wang]

Hi, Hans:

I am using the ConTeXt minimal distribution to run plain TeX.
The ini file is exactly same as your luatex-plain.tex.
However, I run into this problem:

This is LuaTeX, Version beta-0.40.0-2009042221 (Web2C 7.5.7)
 \write18 enabled.
(test.tex (c:/context/tex/texmf-context/tex/generic/context/luatex-basics.tex)
(c:/context/tex/texmf-context/tex/generic/context/luatex-fonts.tex
<luatex-fonts-merged.lua> <luatex-fonts.lua loaded in 0.047 seconds>)
(c:/context/tex/texmf-context/tex/generic/context/luatex-mplib.tex)
! LuaTeX error ...-context/tex/generic/context/luatex-fonts-merged.lua:5124:
attempt to index global 'caches' (a nil value).
<to be read again>
                   \testa
l.1 ...n10-regular                  at 12pt \testa
                                                   \input tufte \par
?

My test file is attached here:
\font\testa=file:lmroman10-regular                  at 12pt \testa
\input tufte \par
\bye

changing the font name to any other file name in the directory won't
solve the problem.
but tfm fonts like cmr10 works fine.

Yue Wang