The -webkit-overflow-scrolling:touch property is reset (and ignored) if the element containing it is hidden with display:none and displayed again.
The reported URL is a basic TC for it. Confirmed with Safari on iOS 5 Beta 6.
Note that this issue happens only when the container contents is an iframe.
This is the related CKEditor ticket: http://dev.ckeditor.com/ticket/8308
Please file iOS bugs at bugreporter.apple.com