You receive an error message when you connect to a mail merge data source by using the Mail Merge Wizard in Word

When you try to connect to a data source while you create a Mail Merge document in Microsoft Word, you may experience one of the following symptoms:

• After you select your data source in step 2 of the Mail Merge Wizard, nothing happens.
• When you use the Mail Merge Wizard, you receive the following error message:
  Word was unable to open the data source.
• When you use the Mail Merge Wizard, and you connect by using MS Query, you receive the following error message:
  ODBC Microsoft Access Driver Login Failed
  
  Could not find file file name.
• When you use Microsoft Visual Basic for Applications code to perform a mail merge with external data, you may receive the following error message:
  Run-time error '9105'
  String longer than 255 characters
  Additionally, when you view the connection string in the Immediate window after you pause your code, only the first 255 characters of the string are displayed.

This problem occurs because Word cannot create a connection string that is longer than 255 characters.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.