Calling a Webdynpro Iview from a Web Page

Hi guys we are trying to display a custom webdynpro iview in a web page.

when the user clicks on a link on the left side navigation in the webpage it is supposed to open the webdynpro iview in an Iframe in the same window beside the left navigation area. but we are getting a warning message before the iview is opened.

an error occured while starting the iview Application/webdynpro/dispatcher/sap.com/pb/PageBuilder:jsessionid=(J2EE3062800)ID484538950DB11873745832264248987END will run with a wrong client window ID!

and when we click on ok the iview is displayed in the IFrame

to open the iview we are using an URL of the format

http://<Server>:<Port>/irj/portal?NavigationTarget=navurl://8bc08160d466f592c481da5639ca31e9&NavMode=3

can any one tell me why we are getting this message and how to remove it.