If you look at the headers, the URL without the word "management" in it is 301 redirecting to the URL with the word management. In all likelihood, you manually edited the permalink and created a page with a similar URL and the combination of those 2 events confused WP, which tries to set up a redirect in the event the permalink is changed.
Try looking at your DB in the posts table and find the record for the URL without the word "management" and look at the guid field.
Too much playing with permalinks (manual or otherwise) can create redirect loops that will make your browser's head spin.
Hope that helps.