Often when I click broadcast and then Skype is hijacked, I have no sound, in other words, I can hear the tone that Skype has started but when I talk, my meter in Nicecast does not move and I do not have an echo. I am not broadcasting. I now know to check first that the audio device is selected. Even if it was selected, it appears that when Skype launches (is hijacked) Nicecast looses the audio device that you have carefully chosen when you first opened it.
I've been thinking that it's a conflict and trash the skype preference in the library of the root user but then the whole computer needs to be restarted. Worse yet, sometimes that seems to not resolve the problem. Well, now I realize that it is not even the problem - just make sure that your audio device is still selected! Thank you Lee!