If you have disabled netCut from automatic running, when you run netcut manually . you will see following window pop up
uac.png [ 20.73 KiB | Viewed 11702 times ]
Reason you see this pop up as netCut require to control low level network card setting. and can only run under Admin right.
Click on 'Yes' to enable it
uacyes.png [ 24.3 KiB | Viewed 11702 times ]