Thanks for your help.
I have Pages 09. No, the files are not corrupted, and can be opened with TextEdit (which i hate having to use). The problem is exactly as you understood: I go into Pages '09 and start with a blank document, then save it as .doc, and when I come back to it later Pages will not open it. Pages will not open ANY .doc file at all, whether created in Pages & saved or created in Word and copied to my computer. This is unusual, right?