Rad Window Telerik Control not displaying correctly on first display

I am working on an ASP.Net Project. I am using Rad windo开发者_StackOverfloww PopUp On a page.This opens on click on button.

But i am facing one problem. When the page loads for the first time,this window is not opening properly, i.e. some content missing for the first time on this window. But second time it show all contents properly.

Please help.