Could be a software conflict or incompatibility.
Brink will know more about it, but some quick things. Do you have another office product installed, such as office trial, office starter, office 2010, etc?
Could your antivirus or other security software/settings be interfering with the download of the program, or the opening process after the download?
Can you repair it by control panel uninstall programs, click it, click change, click repair?