Widgets don’t save

I need to make changes to a widget, but when I do, the grey circle next to the Save button just goes round and round and round. I’ve left it for an hour, and nothing happens. It never saves my changes!

I tried disabling all my plugins but it made no difference. I also tried to use the “Enable accessibility mode”, I made the changes hit “Save” but then it game me a 404 and said “wp-admin/widgets.php” was not found?!

What’s going on?

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