“The page at https:/widgets.wp.com says request failed, error 404”

I keep getting this popup error message when I am editing the page http://bitcoinfortunebuilder.com/non-conventional-analyses/

“The page at https:/widgets.wp.com says request failed, error 404”

I have no idea where this is coming from, does anyone else recognise what is causing this? It is really nerving!

The page I need help with: [log in to see the link]