Older versions of FPW Post Thumbnails ( now part of FPW Category Thumbnails ) did not provide turning off display of current theme's thumbnails. The only solution was editing theme's templates to remove or comment out calls to the_post_thumbnail() function ( contrary to author's promise that modifications of the current theme is not needed ). Recent versions FPW Category Thumbnails ( 1.6.4 and up ) finally provide this functionality. There is an option Hide output of the current theme's the_post_thumbnail() in FPW Post Thumbnails. Check this box, click Update button, and it's done. Once set, you don't even need to have FPW Post Thumbnails enabled.
