Problem:
In Microsoft Outlook 2007, if you use Quick Text Hotkeys text will keep adding itself until the email is full.

Cause:
The reason for this happening is because the hotkey assigned is already being used by Microsoft Outlook as a default key combination.

Solution:
It is recommended that you change the hotkey that the Quick Text is assigned to to a different key combination. For a list of default Outlook hotkeys, visit the following link:
http://office.microsoft.com/en-us/outlook/HP012303961033.aspx