I have one user that uses Word 2003 upon close it will usually crash saying that it wants to recover the document, it starts to close and crashes again. This is described perfectly in KB917688 the article goes on to say that MSO.dll is bad or corrupt. Microsoft provides a patch for this, which you unzip. I placed mine in the root drive and executed from there, I pointed all the default destinations to the C root drive as well. This patch went through to what looks like a reinstall, I did it a second time and ran the repair utility from the patch. The program still crashes.
I've done the obvious, uninstall, reinstall and load all the latest service packs, cleared cache and defragged as well.