[texworks] typeset problem: File `ERROR:Systemcommandexecutionisdisabled(seePreferences).sty ' not found

[Jian Lin]

Hello,

I'm running TexLive 2012 on MAC Mac OS X 10.7.5.
I used to simply press "Command+T" to typeset my .tex script. 

But now it shows "! LaTeX Error: File `ERROR:Systemcommandexecutionisdisabled(seePreferences).sty
' not found.Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: sty)"

This means I also need to press "enter" to complete the typeset. 

Can you please tell what is the problem, so I can avoid pressing the "enter" key.

Thanks !
 
----- configuration info -----
TeXworks version : 0.4.4r1004 (release)
Install location : /Applications/TeX/TeXworks.app
Library path     : /Users/jianlin/Library/TeXworks/
pdfTeX location  : /usr/local/texlive/2012/bin/x86_64-darwin/pdftex
Operating system : Mac OS X 10.7.5 (Darwin Kernel Version 11.4.2: Thu Aug 23 16:25:48 PDT 2012; root:xnu-1699.32.7~1/RELEASE_X86_64)
Qt4 version      : 4.8.1 (build) / 4.8.1 (runtime)
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