Updating fail to download or complete. When you check the updating log the following message is shown:
com.sophos.autoupdate: Error:
Could not update Sophos Anti-Virus at [TIME] on [DATE]
com.sophos.autoupdate: Verification failed com.sophos.autoupdate:

The files downloaded by Sophos AutoUpdate are corrupt or incomplete.

    1.    Open Terminal from Spotlight

    2.    Paste in the following command and press enter

sudo rm -rf /Library/Caches/com.sophos.sau/ ; /usr/bin/SophosUpdate

You will be prompted for your account password. Type the same on you use to unlock system preferences panels etc. - the password will not appear on screen. Press enter once you have entered the password.

The command will clear all of the already downloaded files in the sophos autoupdate cache and force a new download.

If the problem continues something is interrupting the download files and when sophos autoupdate checks the files it sees a problem with them. Common causes are a proxy or similiar scanning the internet traffic.