However I still get the same problem as b*cat if I click the "View/Save" Button.
Using Windows 7 & Firefox
The popup graph is displayed by one of the few 3rd party utilities there is in MDWS as I couldn't get anything to work myself. I've asked the author but no response so may have to look elsewhere for something. It only seems to happen under certain circumstances though and I don't know what they are - yet.
Later.... Just had a quick look as I see you are using Firefox as is b*cat (tend to avoid it as it keeps crashing) and yes, that black area is exactly what I see. Can you try Chrome or Opera (Chrome based now) please if possible and see what happens? Thanks.
Also, IE11 (which I hardly ever use as it's so quirky) seems to not want to display popups of Graphs here even with the popup blocker turned off (it does display the Options menu though)....