Try each of the following steps in order until the issue is resolved:
 
     
    • Grant the user the appropriate NTFS rights
    • Grant users Full control to the following registry keys:

      HKEY_CLASSES_ROOT\Word.Application\CLSID

      HKEY_CLASSES_ROOT\CLSID\{000209FF-0000-0000-C000-000000000046}\LocalServer32
     
    • Run FileMon to look for any permission denied messages and grant the appropriate rights as needed
     
    • Ensure Microsoft Office is installed locally on each workstation
     
    • Recreate the Donor Acknowledgement letter parameters