Forgive me if you already know this, I'm simply trying to cover my bases. Is it possible that you turned hyphenation off for one affected document, but not for others? Since this setting is document-specific, you will need to turn off hyphenation for each problematic document, and save the document so that the setting is remembered the next time the document is opened.
If you have already turned off hyphenation in all affected documents, and resaved them, I'm not certain what else it could be. You may also want to ensure that you have SP3 installed. The version number displayed in the "About WordPerfect" dialog should be "188.8.131.522" or greater. You can find WPO 12 service packs here:
Hope that helps,