Torbutton blocks use of proxy port 9150 when running more than one instance of TorBrowser
Torbutton v 1.9 4.5
When multiple instances of TorBrower are opened following a successful connection to the Tor network, Torbutton blocks any requests to port 9150 of the non-initiating TorBrowser instances.
When Torbutton is disabled port 9150 can be reached by the non-initiating TorBrowser instances.
Trac:
Username: torbutton_q