One more possibly related bug is issue2320 where subprocesses are 
spawned from multiple threads.  They found an interesting workaround 
that I found seems to help our problem too: "on Windows, if close_fds 
is true then no handles will be inherited by the child process."  So if 
I change the subprocess.Popen lines in my most recently uploaded script 
to:

rc = subprocess.Popen('cd.bat . > blah.txt', close_fds=True).wait()
rc = subprocess.Popen('del.bat blah.txt', close_fds=True).wait()

The rollover logging failure goes away.  Does os.system have a similar 
option?  If not, then that would mean I'd have to convert all os.system 
calls to subprocess.Popen and add the close_fds=True parameter to it.  
The problem with this is that "Note that on Windows, you cannot set 
close_fds to true and also redirect the standard handles by setting 
stdin, stdout or stderr" and I am using both stdin and stdout on my 
main subprocess.Popen call and I have a couple of os.system calls as 
well.  Thoughts?