Is Windows fully updated through Windows Update and do you have the latest drivers installed for your webcam?
Also, it sounds like the iCamSource window may be hidden. When you close the iCamSource window, the iCamSource program still runs in the background. If the iCamSource window is hidden, there will be a small iCamSource icon in the System Tray (Windows). The icon is a small version of the iCam icon (camera lens). From this icon, you can stop, start, or quit iCamSource. If you select "Preferences" it will display the iCamSource window.