ASP. NET webresource.axd error (webform_dopostbackoptions is undefined)

Question

Recently, we have moved the Application  from IIS 5.1 t o IIS 6.0 .We are getting the above javascript error .Any idea on this. As i understood from web ,Actually, in ASP. Net  2.0 ,the validation controls are validated through new http  handler  webresource.axd.In iis,  the .axd extension is mapped to the aspnet_isapi dll.