Hi Colinest84,
Uninstalling & reinstalling rarely achieves anything that a repair won't fix.
It's possible Word is using a corrupt Normal.dotm or Normal.dotx file. These files aren't deleted when you uninstall Word. If you rename or delete them (with Word closed) and re-start Word, that might fix the problem. Word will create a new Normal.dotx file upon restarting. To find where these files are stored on your system, go to Word Options|Advanced > File Locations and look in the 'user templates' line.
As for the registry key, which is another possibility, see:
http://support.microsoft.com/kb/940791