Screenflow distorting desktop audio

Hi everyone, so basically having a really frustrating problem with the Screenflow application. I started a topic in the developers own forum but not having any real success so far, so im hoping that I could possibly find someone who could help me.

Heres a summary of the issues and information :

I am running on an early 2009 imac running OS - 10.8.2

I am trying to record minecraft using screenflow however trying to use my Blue Yeti microphone with the software seems to be causing a problem.

When I record without using a mic, or with the built in mic or from my usb headset the sound recorded from the computer comes back clear and fine. But when you try to use my condenser microphone in my case a Blue yeti. The audio recorded from the computer comes back garbled and distorted. The main reason I purchased the software was specifically for this purpose and at £70 not cheap. So I really would appreciate some sort of advice and solution to this issue I tried it seems strange that the microphone would be causing this problem?

this is an example of how its sounding : http://www.youtube.com/watch?v=03HJ1dTZem8&feature=youtu.be

Lastly I know on the recording the volume of the mic etc isnt very loud i was just rushing these out on the day. Its just to illustrate whats happening.

Really hope anyone has experienced this or has some suggestions thanks guys