Letter Merge Error : XXX.doc is a Mail Merge Main Document. Word cannot find its Data Source

User is prompted with an MS Word alert when trying to open a Word document from a Letter Merge.

 

These alerts are caused by any of the following:

a. Your data source is not located on your computer--for example, the data source is located on a network drive.

b. Your data source is a text-based file, such as *.txt.

c. Your local intranet security settings in Microsoft Internet Explorer do not trust the location that contains your mail merge data source.

To work around this problem, either trust the location in Microsoft Internet Explorer that contains your data source or move the data source locally. Save the data source file either on your Desktop or C:)

Reference: http://support.microsoft.com/kb/834699