Solution by Event Log Doctor

Problem:

After downloading phases completed Autoupdate fails to install the spam rules package. In the logfile error code 80041f04 is displayed.

The folders: datatemp and bintemp are created in C:\Program
Files\Sophos\PureMessage\ folders.

The problem occurs due to a lock. 'inetinfo.exe' keeps the spam rules locked.

Solution:

Stop all services related to PureMessage
Stop all services related to IIS.

Delete datatemp and bintemp directories created by the failed update process.

Right click on the shield and select Update Now - this time the update should succeed.

Start IIS services
Start PureMessage services.

Note: Stopping Simple Mail Transfer Protocol service only is not enough as it leaves a running instance of 'inetinfo.exe'.