Multicam Capture - cannot start webcam...

[camshy23+]

I am using two external webcams and Multicam capture. It says it cannot start the second webcam and for me to try closing other programmes that might be using it. I have checked everywhere that might be using a webcam and cannot see anything! I paid for an Upgrade to Full-Featured MultiCam Capture, thinking it would maybe unlock the full compliment of cameras but it seems not. I am new to this so would appreciate any suggestions. I thought I could record more external video sources than just the one external webcam??