You are dealing with a difficult piece of Word2007/2010 called placeholder text. See:
http://www.shaunakelly.com/word/word...evelopers.html
I've had the best success by editing the placeholder text while is design mode (select the text only. No leading or trailing text). If you want to change the existing text start at the second letter then go back and delete the first. Then close design mode and edit the content control text by selecting the tab. This will make your placeholder text appear changed as well until you delete the text displayed and exit the control. When you do that the placeholder text "should" reappear in the corrrect format.