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== os.popen ==

os.popen() doesn't work when the CWD is a UNC path like
{{{\\hostname\dirname\...}}}.

The call to os.popen() will
appear to succeed, but subsequent calls to read/write the
returned pipe will result in an {{{IOError: invalid parameter}}}
exception.

This failure is not specific to py2exe as it will happen
anytime os.popen() is used with a current working directory
(CWD) that is a UNC path such as {{{\\hostname\dirname\...}}}
rather than a DOS style path such as {{{G:dirname}}}.  While
this isn't specific to py2exe, the problem is rarely
encountered unless a program has been distributed using
something like py2exe and is being executed by clicking on a
file or shortcut to which the user has browsed on the network.

The underlying problem is due to a "feature" in cmd.exe
documented at http://support.microsoft.com/kb/156276/EN-US/

The solution is to use subprocess.Popen() with shell=False
(which won't use cmd.exe) instead of os.popen() (which does use
cmd.exe).  However, subprocess.Popen() has its own 
Windows-related bug which requires working around. See the
subprocess documentation at
http://docs.python.org/dev/lib/module-subprocess.html for
general usage and Py2ExeSubprocessInteractions page for
examples on working around subprocess.Popen bugs that show up
when using py2exe.