The state information is invalid for this page and might be corrupted. error

good days.
i wrote js codes in the aspx page. i have a variable in js codes. and js value is a aspx value. (from database)
my method;
in js codes i wrote
var text=<%=hiddentext.Value%>;
hiddentext is a hiddenfield control of webforms.
and in the page load event my code is;
hiddentext.Value="'"+dbobject.gettext()+"'";
page loads. there is not a problem. but at the postback i have an error message. it is.
The state information is invalid for this page and might be corrupted.
i closed viewstate but there is an error again. 
What must i do?
Thanks.