Scan will not proceed.

I think I understand:  You select 'Scan This Mac', the software looks at the whole drive and starts 'Calculating...' the items to scan but it never completes this step and so the scan doesn't start.

How long did you leave it?

You could try a few things:

• Reboot and try again (if this is a fresh install).
  
  
• Run a repair of the disk from Disk Utility ('Applications' folder, then 'Utilities' folder).
  
  
• Configure the 'Scan This Mac' to not scan all local drives and also exclude compressed files.  Watch the video on scanning:
  
  
  
  
• If all else fails create a custom scan of the whole hard drive.  You mention creating a custom scan but is that of the whole hard drive (i.e., '/')?

There is a similar post here: http://openforum.sophos.com/t5/Sophos-Anti-Virus-for-Mac-Home/Scan-this-mac-will-never-complete-scanning-a-folder-actually/m-p/14081/highlight/true#M6604

I think I understand:  You select 'Scan This Mac', the software looks at the whole drive and starts 'Calculating...' the items to scan but it never completes this step and so the scan doesn't start.

How long did you leave it?

You could try a few things:

• Reboot and try again (if this is a fresh install).
  
  
• Run a repair of the disk from Disk Utility ('Applications' folder, then 'Utilities' folder).
  
  
• Configure the 'Scan This Mac' to not scan all local drives and also exclude compressed files.  Watch the video on scanning:
  
  
  
  
• If all else fails create a custom scan of the whole hard drive.  You mention creating a custom scan but is that of the whole hard drive (i.e., '/')?

There is a similar post here: http://openforum.sophos.com/t5/Sophos-Anti-Virus-for-Mac-Home/Scan-this-mac-will-never-complete-scanning-a-folder-actually/m-p/14081/highlight/true#M6604