script error of Sys.WebFrorms.PageRequestManager

[BLADE]

In my Site, some pages report script error:
 
Sys.WebForms.PageRequestManager undefined.

Other page is ok,no error.

In these pages with error,  used master page,  kicked my scritp.
Ether i use Ajaxpanel or Ajaxmanager, the error always here.
I try move the AjaxControl to any level, the erroe always here.

I  read out zhe AjaxScript   "<script src="/SBB/WebResource.axd?................"
and write into my page like <script src="/sbb/ascp.js" type="text/javascript" ></script>
The error become to :
Sys.ArgumentTypeException: Object od type 'Sys._Application' cannot be converted to type 'Sys._Application'.
Parameter name: instance

So, i need help.

My English is so poor. Don't fun me, please. Thanks.
Oh , this error happened in our 3 coder. we edition is  2008Q1 515.

[Maria Ilieva]

Hi BLADE,

Please let us know if the problem occurs if you are using regular asp UpdatePanel instead of RadAjax.
Also please review the following forum post which discuss this problem.

Best wishes,
Maria Ilieva
the Telerik team

Check out Telerik Trainer, the state of the art learning tool for Telerik products.

[BLADE]

IS OK!\
Thank you Very Much.
TELERIK are the Great Controls.