Situation: A client had a handful of users where the CRM buttons were missing from the Email, Task, and Appointment forms in Outlook. In other words, the user creates an Outlook Appointment, but is unable to track it in CRM because the "Track in CRM" and other buttons are missing from the toolbar.
In this particular case, it was determined that the user's PC came preloaded with Office 2007. The client had uninstalled Office 2007 and installed Office 2003 and then reinstalled the Outlook Client. Other users in the office have Office 2003 and did not have the same issue.
It was determined that this was a common theme among users where the CRM buttons were missing from the Outlook forms. After reinstalling Office 2007 along with the Outlook Client on the offending machines, the buttons were there as they should be on the Outlook forms.