[Dashboard] connecting to dashboard plugin leads to "404" page

I've been using your services for over a year now and I have the dashboard plugin installed and running successfully on all the sites in my account. Lately, on this certain site, whenever I try to go to the dashboard in the admin, for some reason I get to a "404" page. It doesn't happen in any of the other sites I have this dashboard on, and not in any of the other features and plugins on this site.
I've noticed that the URL for this plugin in the admin of this site is: http://goral.outsitedev.com/wp-admin/admin.php?page=wpmudev, and for example, the URL for another plugin that I have installed is: http://goral.outsitedev.com/wp-admin/admin.php?page=fusion-builder-options. So, the basic location where these two plugins are accessed and managed are the same (with a small difference in the related page of course, but the one for the WPMUDEV dashboard plugin leads to a "404" page, for some reason, as described.
I should also mention that I have already removed this plugin and reinstalled it, but that doesn't do the trick either.