Have you checked for viruses - specifically macro viruses in Word? Can you open your document using another/alternative editor? Does it happen in a specific doc or just a particular doc/s? Another way you can check assuming you can still open Word - try bringing up the MS Visual Basic interface (alt-F11) when you open Word. Check if there are any modules/macros active - don't forget to also check on the normal.dot template (known to be infected by some viruses historically). Another way to go is to completely uninstall and re-install Word. This assumes that your program is bad and not the doc.
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