How long are you waiting for the scans to complete. Sometimes the scan seems to be stuck, but things are still going on in the background.
Try going to the Recovery Tab in NU16. From there click on Repair Drives. From there you can check each drive individually. I would suggest the Surface scan option on your system drive, and check the box to Perform on Reboot. That way, no running Windows processes can interfere with the scan.
This scan should check for bad sectors that could be causing the hangs when a regular scan is trying to read a bad sector.