We were a few version behind on WWWC and recently upgraded to WWWC 5.64. After the upgrade our wwModalDialog boxes started to render at the bottom left of our pages. I was able to track the problem to a bug in jQuery-ui.js version 1.8.16 and the updated outerWidth and outerHeight functions. The function calls are used in centerInClient of ww.jQuery.js. When these functions where changed to 'getters' and 'setters' a bug was introduced causing them to act as setters and return the jQuery object when calling without a parameter rather than a number value you were expecting in centerInClient.
Below is a link I found discussing the issue:
https://github.com/harvesthq/chosen/issues/763
I was able to fix our problem by changing all of the outerWidth() and outerHeight() calls in ww.jQuery.js to use a parameter of false (outerWidth(false) and outerHeight(false)) but wanted to get your take on the issue and what you thought was the proper solution.
TIA
Mike