Facts:

1- On a single page app, which I have been developing for the last several week, I have a login dialog, as a div with data-role="dialog". I open using js and a call to changePage. All has been working wonderfully so far. 

2- I use the swatch "a"

the problem:

Since 2 days  when I open the dialog with changePage, the overlay is completely white. (instead of dark) 

What I have done 

 A: I narrowed it down to the CSS ui-dialog which specifies background: none !important. If I remove it, everything is fine. 

 B: I have tried specifying the theme on the dialog div ... , on the changePage call .... to no avail. 

 C: I have checked my markup and the HTML goes through htmlLint ... I am at loss. 

If I update the original CSS (which I am trying to avoid at all costs) to remove the background rule on ui-dialog  it sort of works: there must be NO transition  otherwise the white background flashes.

Question: how can I get the background to be and stay dark ?

I must admit that I am running out of ideas, so any fresh input will be appreciated.