LuaLaTeX does not work anymore since last MiKTeX 2.9 update ("fatal format file error")

Question

I just recently updated Miktex via the update wizard, and after that LuaLaTeX fails to generate any output. At first I thought it would have to do something with SIunitx, because I received an error there and it was used in the file I tried to employ LuaTeX on (SIunitx, was located into another package I think), but that wasn't the case. (SIunitx still doesn't work, because MiKTeX reports

"Message: Unknown archive file size.
Data: expl3
Source: libraries\miktex\packagemanager\internal.h
[...]"

when I try to get expl3 via the package manager.

Anyway, I then tried to use as few packages as possible to rule out some incompatibilities introduced by the new update or something like that, and tried to use LuaLaTeX on the following file:

\documentclass{minimal}
\begin{document}
Test
\end{document}

And all I get is

This is LuaTeX, Version beta-0.70.1-2011052811 <rev 4277>

<Fatal format file error; I'm stymied>

No log-file, no output, nada, only this error message. pdfTeX and the latex-dvips-ps2pdf-way both work without any problems (at least on the above file).

I could really use some help, since everything worked just fine about two weeks ago until my last update.

Please let me know if you want to get further information or anything like that to help me with my problem.

Oh, I almost forgot (in case it's important):

OS: Windows Vista Home Premium (32bit),

MiKTeX 2.9 (just updated :/)

---

I don't know whether I should make another separate question out of this, but I've got another problem with luatex, but only indirectly. I think I already know the cause, so I, more or less, just want to verify whether this is an issue of my own local installation, or a "global" problem:

Not a long time ago, there was another MiKTeX-Update, so I updated. But then I tried to compile another document with lualatex that worked before, but lualatex didn't create a document at all, while not reporting any real problems (at least not via Texmaker). So I looked into the folder of the file, and voila, lualatexor luatex(:O) created a folder, named "luatex-cache" and a log file, but nothing more. I then tried to isolate the problem by making a minimal example and first found out, that it probably isn't a luatex-problem itself, since sth. like:

\documentclass{minimal}
\begin{document}
Test
\end{document}

was compiled without any problems. I then continuously added more packages and I think the troublemaker could be luatextra. Again, the only output of

\documentclass{minimal}
\usepackage[T1]{fontenc}
\usepackage{luatextra}
\begin{document}
Test.
\end{document}

was: a folder named "luatex-cache" with an empty subfolder named "generic" and a log-file. The last 4 lines of the log-file can be seen below (I hope these are sufficient):

.
.
.
Lua module: luaotfload 2011/04/21 1.25 OpenType layout system.
luaotfload: loading file C:/Program Files/MiKTeX 2.9/tex/luatex/luaotfload/otfl
-luat-dum.lua.
quiting: fix your readable cache path

If the moderators think this is important enough to post it as a separate question, I'm happy to do that. :D

Answer 1

I wrote about this bug to the maintainer of MiKTeX about two weeks ago, but got no answer.

Thus I installed TeX Live 2010. If you know what you are doing, you can do this:

1. Start the installation process of TeX Live 2010. Wait until it created all the folders. Abort the installation.
2. Copy all the LaTeX packages and the respective documentation from MiKTeX to the corresponding folders of TeX Live.
3. Start installation process again.
4. Afterwards get the update of luatex from tlcontrib.

Answer 2

I encountered the same problem before. When I downloaded the latest unicode-math packages from GitHub, it worked fine. I don't understand the connection, and it may be specific to my computer, but you can give it a try.

Answer 3

I had the same problem with Miktex 2.9.

I use Windows 7.

I fixed it by setting an Environment variable named TEXMFCACHE which in my case to

c:\Users\Admin\AppData\Local\Miktex\2.9.

It worked.