Interesting, the json output you posted gets parsed ok here and obviously it complains about an error at char 1309, though the string you posted is only 1308 chars long.
It sounds like the json output from cgminer has some extra whitespace or linefeed but then again the json module should be able to work with that just fine.
I am a bit lost here, could you please pm me or post the complete output of the following command(s):
sudo apt-get install netcat-openbsd
echo "{\"command\":\"stats\"}"| nc 10.0.100.141 4028
The above installs the networking swiss army knife 'netcat' and uses netcat to fetch the json output directly from cgminer api port of your miner so that I can see what could failing here when reading it from my script.