SP dialog issue in application page with update panel

<p>Hi,</p><p>I have Sharepoint 2010 application page which is&nbsp; called from ribbon custom button action. This application page has update panel and button &amp; grid&nbsp;are inside the update panel.</p><p>Actually, when i click the button, it should popup another page. but now SPdialog is not open and no error in 14 logs or in UI. (i've tried with scriptManager.Registerstartupscript &amp; scriptManager.RegisterClientscriptblock)</p><p>Some sharepoint sites, it's working perfectly. Some of them not. When i view the source, I dont find sp.js, sp.runtime.js are not there. (Event after i added scriptlink in respective pages).</p><p>Couldnt figure out the issue. Kindly advise. </p><p></p><p></p>