hi eric,
first of all i should say i was not running any server-client.I had both the pages(parent and pop-up) as htmls.the error message i was getting was a javascript error which read as:-
the server threw an exception.
but when the same command(window.opener.document.showSlaUserDetails.otherBox.options[len] = newOpt
is written on the parent page itself without window.opener then it works perfectly.but in popup it says the above said error.
the server threw an exception