You might want to try repairing office.
http://support.microsoft.com/kb/264625/en-us?FR=1&PA=1&SD=HSCH If that does
do it, you might want to try the additional steps below or go to the office
news group for expert help.
Check your "event view" for any error messages or warning in your
application and system log. Check your "device manager" of any warning or
errors. Clean your hard drive. Run a "virus check"and "anti-spyware" scan.
Check that your Operating system is up to date with all security patches and
other patches pertaining to other software that you have on your machine by
running "windows update"