Refreshing a crystal reports (asp.net/c#)

Question

I deployed my website in IIS 7.5, when i click on the button to open the page that contain the crystal report, i get a blank page for the first time,but when i refresh the page it's ok. it's happened just for the first load, i tried crystalvieweer.RefreshReport() how can i fix this problem ?
 
please help me.Thanks in advance.