当我尝试使用\sfrac（从xfrac包中）时，会产生多个错误missing number, treated as zero。illegal unit of measurement (pt inserted)
示例文档：
\documentclass{article}
\usepackage{xfrac}
\usepackage{fix-cm} % Fixes warnings about missing fonts; see http://tex.stackexchange.com/questions/32378/xfrac-siunitx-gives-me-a-font-warning
\begin{document}
Test $\sfrac{1}{2}$.
\end{document}
这会产生八个错误，全部发生在使用的位置\sfrac（一半是“缺失数字”错误，另一半是“非法单位”错误）。
我正在使用 TexMakerX 2.1 和 MikTeX 2.9。如能提供任何关于如何解决此问题的建议，我将不胜感激。
\listfiles编辑：根据要求，以下是的输出：
*File List*
article.cls 2007/10/19 v1.4h Standard LaTeX document class
size10.clo 2007/10/19 v1.4h Standard LaTeX file (size option)
xfrac.sty 2011/10/09 v2896 L3 Experimental split-level fractions
amstext.sty 2000/06/29 v2.01
amsgen.sty 1999/11/30 v2.0
graphicx.sty 1999/02/16 v1.0f Enhanced LaTeX Graphics (DPC,SPQR)
keyval.sty 1999/03/16 v1.13 key=value parser (DPC)
graphics.sty 2009/02/05 v1.0o Standard LaTeX Graphics (DPC,SPQR)
trig.sty 1999/03/16 v1.09 sin cos tan (DPC)
graphics.cfg 2007/01/18 v1.5 graphics configuration of teTeX/TeXLive
pdftex.def 2011/05/27 v0.06d Graphics/color for pdfTeX
infwarerr.sty 2010/04/08 v1.3 Providing info/warning/message (HO)
ltxcmds.sty 2011/04/18 v1.20 LaTeX kernel commands for general use (HO)
l3keys2e.sty 2011/10/09 v2900 LaTeX2e option processing using LaTeX3 keys
xparse.sty 2011/10/09 v2900 L3 Experimental document command parser
expl3.sty 2012/07/16 v3990 L3 Experimental code bundle wrapper
l3names.sty 2012/07/16 v3990 L3 Namespace for primitives
l3bootstrap.sty 2012/07/15 v3986 L3 Experimental bootstrap code
etex.sty 1998/03/26 v2.0 eTeX basic definition package (PEB)
l3basics.sty 2012/07/15 v3987 L3 Basic definitions
l3expan.sty 2012/07/15 v3986 L3 Argument expansion
l3tl.sty 2012/07/15 v3986 L3 Token lists
l3seq.sty 2012/07/15 v3986 L3 Sequences and stacks
l3int.sty 2012/07/15 v3986 L3 Integers
l3quark.sty 2012/07/15 v3986 L3 Quarks
l3prg.sty 2012/07/15 v3986 L3 Control structures
l3clist.sty 2012/07/15 v3986 L3 Comma separated lists
l3token.sty 2012/07/15 v3986 L3 Experimental token manipulation
l3prop.sty 2012/07/15 v3986 L3 Property lists
l3msg.sty 2012/07/15 v3986 L3 Messages
l3file.sty 2012/07/15 v3986 L3 File and I/O operations
l3skip.sty 2012/07/15 v3986 L3 Dimensions and skips
l3keys.sty 2012/07/15 v3986 L3 Experimental key-value interfaces
l3fp.sty 2012/07/15 v3986 L3 Floating points
l3box.sty 2012/07/15 v3986 L3 Experimental boxes
l3coffins.sty 2012/07/15 v3986 L3 Coffin code layer
l3color.sty 2012/07/15 v3986 L3 Experimental colour support
l3luatex.sty 2012/07/15 v3986 L3 Experimental LuaTeX-specific functions
l3candidates.sty 2012/05/12 v3633 L3 Experimental additions to l3kernel
textcomp.sty 2005/09/27 v1.99g Standard LaTeX package
ts1enc.def 2001/06/05 v3.0e (jk/car/fm) Standard LaTeX file
xtemplate.sty 2011/10/09 v2900 L3 Experimental prototype document functions
fix-cm.sty 2006/09/13 v1.1m fixes to LaTeX
ts1enc.def 2001/06/05 v3.0e (jk/car/fm) Standard LaTeX file
supp-pdf.mkii
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