hello I am trying to connect more than one usb camera to record on my computer, and I bought four cameras sirius 12mp, usb hub and cable with amplifier.These cameras are plug&use and when I conect usb hub and four cameras works normaly.When I add cameras to Active web cam and other programs first camera works good and recording but when I plug second camera the screen become black and show me:

12/2/2009 22:02:57, Camera 2: Error 8007001F: Cannot run preview graph!

If anyone know what is the problem help me! thanks