Help: Mac User - Error message: "A scan cannot be completed. An error occured running the scan "Scan Local Drives"

Hi there,

I need your expertise on something. 

I have Sophos installed since ages on a mac OX version 10.9.5 - it was working very well -  I think the last scan was a few weeks ago. 

Now, when I open Sophos and I click on "Scan" > the blue bar gets filled up very fast then > " "A scan cannot be completed. An error occured running the scan "Scan Local Drives" " message appears. 

I have updated sophos - switched off/on my machine, cleared the trash etc... but it's still not working.

Do you have any idea where the glitch could come from? What should I do?

I don't like not being able to scan and check my machine. 

Thank you very much

M.