You wouldn’t happen to be using .doc files, are you? I did some digging around in the OpenOffice issue tracker, and found this bug: http://documentation.openoffice.org/...g.cgi?id=74537
It says that with .doc files, the word count would display old numbers unless the program was restarted. Which sounds a lot like what you are experiencing.
That bug, among a few others, indicate that OpenOffice has been known to exhibit some strange word counting behavior with .doc files. Try saving with the standard OpenOffice format, .odt. If you already are using .odt, then I have no idea what to suggest. Good luck!