How did it work on your desktop computer, and what was the CPU usage?
It sounds like the motion detection and other image processing is too much for your computer's hardware, and that's why the frame rate is slower.
Have you tried closing the iCamSource window to hide it to see if that has a positive affect on what you see on iCam when zoomed in? If the image is not being resized and displayed that will use less CPU, although not that much less, probably.