Loading usercontrol from the menu gives javascript errors--Any idea?

I have an asp.net page that has menu which loads user control dynamically when the menu item is clicked.Now in the user control i have some buttons calling javascript on clientClick.When i click this button,it throws javascript error
Microsoft JScript runtime error: '(function name)' is undefined  
Here is the code snippet:
 function CheckUpload() {
        var flag = validatePage();
        var Checktext = $("#HyperLinkUploadFile").val();
     
        if (Checktext != '' && flag)
            flag = true;

        return flag;
  ...