Live Streaming Equipment?
 

So I am wanting to run a live web broadcast through U Stream using 4 cameras. I have the basic USB plug in Webcams. I also have a Sony MiniDV cam which works as a webcam through the firewire. And I also have a Panasonic DVX100A which would probably also work through firewire.

Basically, I am wondering what equipment or tools would I need to get 4 cameras streaming at once? I have Ustream Producer Pro but when I bought a USB Hub, it only showed 1 camera while the rest were blue screens. I tired plugging all 4 cameras into my iMac without the usb hub and only two cameras would work. I am wanting to do this live stream using my MacBook Pro. But could use my iMac to do so if needed.

Do I need a splitter? Video Mixer? Clueless on this. Thanks for your help and suggestions ahead of time!