Still active after disabling plugin

Hello there,

I don’t know whether this is an issue with the plugin, or some form of caching. Anyway, my employer’s website is http://www.esbgc.org. When I visit it in a browser in which I have not logged into the WP admin, the site is still behaving as if the plugin is installed – take http://www.esbgc.org/early-years-services/, for example; works fine when I’m logged into the admin in one browser, but is showing category posts in another where I am not logged in. I have emptied the browser’s cache, deactivated the caching plugin I had been using…

Any suggestions?

Best wishes.

http://ww.wp.xz.cn/plugins/wp-no-category-base/