Winword /a starts Word in Safe Mode: basically this is Word in its default
install mode bypassing all macros, add-ins, templates, customizations, etc.
This indicates that there is nothing wrong with Word but there is an add-in
causing the problem. I suggest that you first eliminate a normal.dot problem
by renaming it as normal.bad, which will let you recover anything important
from it later once the problem has been isolated.
If the problem persists with a new normal.dot, then check for third party
add-ins and macros. You'll find macros listed under Tools, Macros. For
add-ins, see How to find add-ins:
http://www.word.mvps.org/FAQs/Customization/CheckIfAddinsInstalled.htm
http://office.microsoft.com/en-us/assistance/HA011514521033.aspx