I recommend combining the clear cookies step with a ClearCache(History) step, since the browser could be reloading cached content. If this does not resolve your issue, we will need more information about your test scenario. Please provide us with a copy of your test and access to your application. If it is not possible to grant us access to your application, please take a Fiddler trace and attach it to a support ticket in a zip file. If you are unfamiliar with how to do that please refer to this short video. You can download the Fiddler application from here. A Jing video demonstrating the issue may also help us to better understand what is happening.
the Telerik team