obfsproxy tor browser bundle listens on static ports.
browser_en-US/App/./tor -f /run/shm/obfs/tor-browser_en-US/App/../Data/Tor/torrc DataDirectory /run/shm/obfs/tor-browser_en-US/Data/Tor ControlPort 9051
Which means it won't start if you already have a system tor listening on the same ports.
It would be nice if it used dynamic ports as the normal Tor Browse Bundles do.
Trac:
Username: murble