An issue may occur after a user has carried out a mail merge and they attempt to view the .doc file, a 404 error is returned.
The .doc file was created in the Library. Process Monitor (ProcMon) showed multiple requests to read web.config at the same time as it was looking for the template document. The process that was making the requests was w3wp.exe, and the result was PATH NOT FOUND. The CreateFile requests were to the following directories:
C:\Program Files (x86)\Sage\CRM\CRM\WWWRoot\eware.dll\web.config
C:\Program Files (x86)\Sage\CRM\CRM\WWWRoot\eware.dll\do\web.config
C:\Program Files (x86)\Sage\CRM\CRM\WWWRoot\eware.dll\do\Global+Templates\web.config
C:\Program Files (x86)\Sage\CRM\CRM\WWWRoot\eware.dll\do\Global+Templates\UK\web.config
C:\Program Files (x86)\Sage\CRM\CRM\WWWRoot\eware.dll\do\Global+Templates\UK\MyWordDoc.doc\web.config
The issue was caused by an administrator renaming the web.config from the \CRM\WWWRoot directory. Adding in a vanilla web.config resolved the issue.