Sophos for Microsoft SharePoint: you cannot run an on-demand scan on a single document

Issue
When you try to use Scan Target Settings to select a specific folder or document for an on-demand scan, you cannot see far enough into the folder structure to select the document.

This issue occurs if you have Sophos for Microsoft SharePoint installed on SharePoint 2007, and you upgrade the Windows SharePoint Services 3.0, service pack 1 (WSS SP1) to WSS SP2.

Sophos product and version
Sophos for Microsoft SharePoint installed on SharePoint 2007

Operating system
Windows 2003
Windows 2008

What to do

In Windows Services restart the Sophos for Microsoft SharePoint Worker service.