Thank you for your interest in Telerik Test Studio.
I am sorry to hear you are facing any difficulties. To fully understand where the root cause might be and be able to provide you best solution I will need some further details about the page you are testing.
Let me know more about the kind of pop-up window that is not recorded by Test Studio - is this dialog window or is it sort of a form to be fulfilled. Please elaborate more on your exact scenario. If possible it would be great to provide access to your application or a sample one that reproduces the same behavior.
I am looking forward to hearing from you.