Cannot delete entry in member's profile: 'Recent Activity'

This is the error message I get in multiple browsers when clicking on 'Hide':

CollectiveX :: 404
That page couldn't be found.. if you came here from another site, check the URL and try again; otherwise, perhaps that item has been deleted?
Use the Back Button on your browser to return to the previous page.

The member deleted one of their comments in a discussion thread, then tried to hide/delete it in their own 'Recent Activity' section of their profile, but can't, and neither can I.