Excel Why IMAGE Function Changes To CONNECT Error

Carl Pepperseed, on assignment in the Burmese Jungle, reports that his =IMAGE() function in Excel suddenly started returning a #CONNECT! error. While we all feel bad for Carl, maybe that means that IMAGE is now Dynamic? If we could just figure out what Carl did to bring that #CONNECT! error!
How about F9? No.
How about Ctrl+Alt+F9? No.
How about F2 / Enter? No.
Replace the URL and then Undo? The image is still there.
Copy the sheet within the workbook? No.
How about Copy the Sheet to a new Workbook? That seems to be it.
Which is bad news for the people hoping for Dynamic IMAGE function.