I am having what I believe should be a fairly simple problem, but for the life of me I cannot see my problem. The problem is related to ScriptManager.RegisterStartupScript,
I try many things and finally found that the last parameter must be false and you must add tag to the java script :
string script = "< SCRIPT >alert('hello!');< /SCRIPT>"; ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), key, script, **false**);