I have had problems with Word crashing when I try to open a document, particularly when online and opening a Word document on the file server.  I can usually get it to work if I open Word first and then open a document but even that doesn't work at times.

I finally found a post online mentioning problems with add-ins.  I looked at the add-ins and my Adobe Acrobat installation had installed a PDF add-in, my scanning application had installed 2 PDF add-ins and I had the add-in from Microsoft to create PDF files.  I disabled the PDF add-ins and have not had the problem since. [more]

Also, under Vista,  in order to remove most of the add-ins, I had to have administrative access by running Word as administrator.  There isn't a "Run as administrator" option when I right-click on the short-cut.  I had to find the actual WINWORD executable and right-click on it to run as administrator.