The following bug occurs on OS X El Captain 10.11.6 with Tunnelblick 3.6.5 (build 4566):
-I use my home wi-fi to connect to my VPN server (which is OpenVPN server ran on Linux Ubuntu)
-I quit tunnelblick and disconnect from VPN
-Then I move to location with public hotspot with log in page that is served to anyone who connects to network (like Starbucks or any campus wi-fi)
-In this network, the host on which OpenVPN is running can not even be 'ping'ed (the packets do not reach the destination) despite the fact that TunnelBlick is switched off
-The problem goes away after I restart computer