Please note that the scan only appears to be stuck on 6%. The progress bar does not move due the large size of the folder (up to 20GB) which is being scanned (WinSXS). As you can see in the Details section of the scan, the scanned file is constantly changing. The progress bar will jump to 30-50% (depending on the number of files from your machine) once the folder has been scanned.
Thank you for your replies. I reloaded Bullguard and changed the Windows power options in Control panel to "put the computer to sleep after 2 hours". Before this change it had been set to 15 minutes. Since then the progress bar has moved steadily through the percentage range.