the problem with WIZARD-Control

I have a problem with teh wizar control.

Let us say that I have som textboxes, and dropdownLists, if we fill some information and move forward by pressing "Next-button"

if I want to move back and press the previosbutton on the explorer, then I get the page but with empty textboxes WHY??

 

P.S if I create a simple webpage with the wizard then it works.. But I can't start all over again, pls help me! 
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