Follow these instructions for word 2007 and 2010:
Word 2007: Click on the Office icon and select "Word Options." 
Word 2010: Click on the File ribbon and select "Options."

1. Click on "Add-ins."
2. Change the "Manage" options to "Disabled Items."
3. Click Go.
4. Highlight any EndNote item(s) and click "Enable."
5. Click OK.

If this does not work, you'll find further help at CWYW 1 on EndNote's FAQ website.