I recently installed TeXLive 2011 on my MacBook (running MacOS X 10.6.8) and got the following problem:

Example:

```
\documentclass[11pt, a4paper]{scrbook}

\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[TS1, T1]{fontenc} 
\usepackage{aecompl}
\usepackage{textcomp} 
\usepackage[ngerman]{babel}
\usepackage{xspace}
\usepackage[tight]{units}
\usepackage{varwidth}
\usepackage{xcolor}
\usepackage{amsmath}

\usepackage{siunitx}
%\usepackage[round-mode=places, round-integer-to-decimal, round-precision=2,
%   table-format = 1.2, 
%   table-number-alignment=center,
%   output-decimal-marker={,},
%   group-digits=false 
%   ]{siunitx} 

\newcommand{\FZ}[1]{\ensuremath{\textcolor{blue}{#1}}\xspace}
\newcommand{\ps}{\FZ{p_{\mathrm{s}}}}

\begin{document}
\listoffigures

\begin{figure}
\rule{5cm}{5cm}

\caption{effect of \ps on $p_{\mathrm{s}}$}
\end{figure}

\rule{1pt}{5cm}

effect of \ps on $p_{\mathrm{s}}$ -- here it works

\end{document}

```

With TeXLive 2010 it compiles without a problem.

With TeXLive 2011, I get the following error message after the second pdflatex run:

```
 (./FehlerTeX2011.lof ./FehlerTeX2011.lof:2: Undefined control
 sequence. <argument> ... 0.1}{\ignorespaces effect of \pson 
       $p_{\mathrm {s}}$} l.2 ...aces effect of \pson $p_{\mathrm {s}}$}}{1}

```

There seems to be a problem with the custom command `\ps`, the `siunitx` package and the list of figures, as the error can be **avoided** 

* by deactivating `siunitx`
* or by typesetting `\ps*{}*` in the caption with parenthesis
* or by removing the list of figures
* or by using TeXLive 2010 instead  

(luckily in OS X there is a way to switch between different TeX installations easily)

Can anybody help and tell me what's going wrong?

---

here is the complete log file for used package versions:

```
    This is pdfTeX, Version 3.1415926-2.3-1.40.12 (TeX Live 2011)
 \write18 enabled.
entering extended mode
(./FehlerTeX2011.tex
LaTeX2e <2011/06/27>
Babel <v3.8m> and hyphenation patterns for english, dumylang, nohyphenation, ge
rman-x-2011-07-01, ngerman-x-2011-07-01, afrikaans, ancientgreek, ibycus, arabi
c, armenian, basque, bulgarian, catalan, pinyin, coptic, croatian, czech, danis
h, dutch, ukenglish, usenglishmax, esperanto, estonian, ethiopic, farsi, finnis
h, french, galician, german, ngerman, swissgerman, monogreek, greek, hungarian,
 icelandic, assamese, bengali, gujarati, hindi, kannada, malayalam, marathi, or
iya, panjabi, tamil, telugu, indonesian, interlingua, irish, italian, kurmanji,
 lao, latin, latvian, lithuanian, mongolian, mongolianlmc, bokmal, nynorsk, pol
ish, portuguese, romanian, russian, sanskrit, serbian, serbianc, slovak, sloven
ian, spanish, swedish, turkish, turkmen, ukrainian, uppersorbian, welsh, loaded
.
(/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/scrbook.cls
Document Class: scrbook 2011/06/16 v3.09a KOMA-Script document class (book)
(/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/scrkbase.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/scrbase.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/scrlfile.sty
Package scrlfile, 2011/03/09 v3.09 KOMA-Script package (loading files)
                  Copyright (C) Markus Kohm

))) (/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/tocbasic.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/scrsize11pt.clo)
(/usr/local/texlive/2011/texmf-dist/tex/latex/koma-script/typearea.sty
Package typearea, 2011/06/16 v3.09a KOMA-Script package (type area)
                  Copyright (C) Frank Neukam, 1992-1994
                  Copyright (C) Markus Kohm, 1994-

)) (/usr/local/texlive/2011/texmf-dist/tex/generic/babel/babel.sty
(/usr/local/texlive/2011/texmf-dist/tex/generic/babel/ngermanb.ldf
(/usr/local/texlive/2011/texmf-dist/tex/generic/babel/babel.def)))
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/inputenc.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/utf8.def
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/t1enc.dfu)
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/ot1enc.dfu)
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/omsenc.dfu)))
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/fontenc.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/ts1enc.def
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/ts1enc.dfu))
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/t1enc.def))
(/usr/local/texlive/2011/texmf-dist/tex/latex/ae/aecompl.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/textcomp.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/ts1enc.def))
(/usr/local/texlive/2011/texmf-dist/tex/latex/tools/xspace.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/units/units.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/ifthen.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/units/nicefrac.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/varwidth/varwidth.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/xcolor/xcolor.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/latexconfig/color.cfg)
(/usr/local/texlive/2011/texmf-dist/tex/latex/pdftex-def/pdftex.def
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/infwarerr.sty)
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/ltxcmds.sty)))
(/usr/local/texlive/2011/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/local/texlive/2011/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/siunitx/siunitx.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/expl3.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3names.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3bootstrap.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/etex-pkg/etex.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/tools/calc.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/graphics/graphics.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/graphics/trig.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/latexconfig/graphics.cfg))
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3basics.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3expan.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3tl.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3seq.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3int.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3quark.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3prg.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3clist.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3token.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3prop.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3msg.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3io.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3file.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3skip.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3keys.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3fp.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3box.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3coffins.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3color.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3kernel/l3luatex.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/tools/array.sty)
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3packages/l3keys2e/l3keys2e.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/l3packages/xparse/xparse.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/beamer/translator/translator.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/beamer/translator/translator-lang
uage-mappings.tex))) (./FehlerTeX2011.aux)
(/usr/local/texlive/2011/texmf-dist/tex/latex/base/ts1cmr.fd)
(/usr/local/texlive/2011/texmf-dist/tex/context/base/supp-pdf.mkii
[Loading MPS to PDF converter (version 2006.09.02).]
) (/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/pdftexcmds.sty
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/ifluatex.sty)
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/ifpdf.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/oberdiek/epstopdf-base.sty
(/usr/local/texlive/2011/texmf-dist/tex/latex/oberdiek/grfext.sty
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/kvdefinekeys.sty))
(/usr/local/texlive/2011/texmf-dist/tex/latex/oberdiek/kvoptions.sty
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/kvsetkeys.sty
(/usr/local/texlive/2011/texmf-dist/tex/generic/oberdiek/etexcmds.sty)))
(/usr/local/texlive/2011/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))
(/usr/local/texlive/2011/texmf-dist/tex/latex/beamer/translator/dicts/translato
r-basic-dictionary/translator-basic-dictionary-English.dict)
(/usr/local/texlive/2011/texmf-dist/tex/latex/siunitx/config/siunitx-abbreviati
ons.cfg)
(/usr/local/texlive/2011/texmf-dist/tex/latex/siunitx/config/siunitx-binary.cfg
) (/usr/local/texlive/2011/texmf-dist/tex/latex/base/t1cmss.fd)
(./FehlerTeX2011.lof

```