I recently installed a slew of my normal applications on my personal laptop. Unfortunately this somehow messed up my Office 2007 or at least Word 2007.
Problem: Word does not open documents when I double click on them. Instead it opens up empty. When I close it, it crashes, restarts, and repearts the process until Office Diagnostics kicks in (which doesn't find anything).
Solution: I found this wonderful post on the MSDN forums.
http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=427367&SiteID=17
Basically, rename two folders in your registry. Go to Start button/All programs/Accessories/Run and type in 'regedit' and then follow the path HKEY_CURRENT_USER/Software/Microsoft/Office/12.0/Word . . . . once there, rename the folder called 'data' to 'olddata' and the folder called 'options' to 'oldoptions' (Word will recreate the 2 folders once they do not exist).
Wala! The next time I opened a word document everything was back to normal.