Narrowing down error with Intensity Shuttle

So, I was trying to get my Sega Mega Drive 2 to work through my Intensity Shuttle and Black Magic Media express onto the TV with the Composite cable, but several problems cropped up immediately.

First of all, I wasn't clear on whether to set the project and Control Panel to PAL or PAL Progressive, or to some other setting.
Secondly, even when I tried both, no picture appeared on my computer screen or TV, the sound levels were showing up in Media Express but no sound was coming through the TV except when I pulled out the video cable from the input to the Shuttle.
Thirdly, even when I pulled out the video cable, the sound wouldn't always come through on the TV, unless I moved the cable around some, which leads me to believe it's the Composite cable of the console.
Finally, despite this, when I plug the Mega Drive into the TV with it's Composite cable, it works perfectly with no visual or audio errors apparent.

I'd like an opinion on whether it's the Shuttle, the computer (Even though HDMI signals go through fine), the Mega Drive's cables or the Composite cables I used in the output to TV. It's a difficult problem...

Well, I've narrowed down that it's not the Mega Drive's cable. I just bought a new one, and nothing changed. So, if anyone has any ideas about what settings I should try in Media Express and the Black Magic Control Panel, please tell me. I need some help. My ideas aren't working.