I was having this same type of issue and had to go onto Microsoft website to download the latest fixes for 2007.
Run the application in safe mode and see if this continues. And I mean boot to windows normally, but open the application itself in safe mode by either going to the run line and typing word /safe, or go to start, programs, hold down the control key and select word and answer yes to the prompt to start in safe mode. If the problem does not occur with Word in safe mode, then check the com add-ins. Disable all of them and re-enable them one by one to find the offending one/s.