I had exactly the same problem today with MS Office 2007 running on Vista platform. Removed and re-installed Office 2007 to no avail. Also download a tool to remove all traces of Office 2007 before re-installing. Then decided to try Office 2003 as a test and went a bit further than the initial Word splash screen but hung on the document screen and reporting 'Scanning for Viruses' on the bottom left. I then discovered the Norton Internet Security was not running correctly. I removed the Norton and re-installed and that fixed the original issue. Put Office 2007 back on and all is fine now.