sys.webforms.pagerequestmanagerparsererrorexception problem

Hi i have two server.

1. windows xp (IIS5.0)

2. windows 2003 (IIS6.0)

i use updatepanel.

and i have below problem code from windows2003 server not windows xp.

(pagerequestmanagerparsererrorexception)

but source is same.

Is there any option for IIS?

Summary: same source, but only work in window xp server.