The problem occurs when running a mail merge against more than one contact record (This is a general problem that occurs from any entity). When the mail merge is completed, either via 'Edit individual letters' or 'print', and the option to create activities is chosen, only the first letter will be included in the merged document and have an activity created. We have narrowed the problem down to be only users on a roaming profile, where group policy has created a redirect for the user profile 'Application Data' directory to be on a network drive.