The problem described in this thread was finally addressed (or at least it stopped being a problem), but was reintroduced with Avast 2014.9.0.2021!
Avast 2014.9.0.2021 prevents MS Word from SAVING the file being edited, which results in total loss of the file (since MS Word, like all word processors, saves the work file, deletes the named file, and then renames the work file as the named file). Apparently Avast prevents the rename operation from completing.
Uninstalling Avast 2014.9.0.2021 (via control panel) and re-installing Avast 2014.9.0.2018 "solved" the problem, but 2014.9.0.2021 is unusable for anyone with MS Word 2000 or 2003 (and most likely later versions of Word).
Please address and fix this problem as soon as possible. Thank you.