Creating a collapsible widget adds "ui-corner-top" and "ui-corner-bottom" classes to all "ui-btn-inner" elements in the DOM, rather than just to the collapsible header. Setting the context for which ui-btn-inner to change the class on fixes the problem for me.
Example with 1.0.1: http://jsbin.com/ucijek/4
"Collapsible" in the navbar opens a page with collapsible widgets. When you return to the first page, the corners on the navbar buttons are rounded.
Example with the fix: http://jsbin.com/odexog/2
'restricts addition of top, bottom corner classes to collapsible elem…