Delay between TreeView click and display

I am doing something wrong by Telerik application. When I click on a node in my TreeView it takes 24 seconds for data to appear on the screen. I have profiled the whole process and cannot see when the delay is occurring. This is my first REALLY big application and I need help. I have  eliminated the database  as the cause of my problems.

Please come up with places I can look and diangostics I can use.