Hi Uday,
Thanks for the bug report, I confirm this as a bug. It is fixed in the repository now so it will be fixed in the next release, and it is now fixed on the demo site as well.
I think you could fix it in your copy by edit the /ContactForm/MessageListDialog.aspx file and remove the <portal:ScriptLoader control
Then in /App_MasterPages/Dialog.Master file, set IncludejQueryLayout="true" on the ScriptLoader control
My fix in code was a little different but this solution should achieve the same result.
Best,
Joe