Hey, I'm going through the same troubles. However I did something to enable this but I'm not sure anymore what.
Since nobody answered your question I'll tell you how I probably got there: browsing through the 1000 printed pages before me the only thing possible must have been something to do with 'pump'. I know I did a commend (pump ?) and it gave this tun/tap error and a way to resolve it, I did it and it worked. Small chance this will help you but you never know.
Somewhere else here mentions it's int he network options. Sorry I can't help you further.