Telerik's embedded jQuery bootstrap code was changed so that it now unconditionally reassigns window.$ (and window.jQuery) whenever window.jQuery is undefined, with no check on whether window.$ is already occupied by another library (e.g. Prototype.js, MooTools, or any framework that defines a global $ without defining a global jQuery). This directly reproduces the reported symptom (element.dispatchEvent is not a function inside Prototype's fire()).