When the javascript method showModalDialog() is called from a page
with a domain in the URL, window.dialogAgruments is 'undefined'. E.g.
the call from http://portal:50100/irj/portal works and a call from
http://portal.domain.de:50100/irj/portal doesn't work.

Calls of showModalDialog() before FF 3.6 worked without problems.

Can anybody help?

For example call with:
var sFeatures = 'dialogHeight: 200px; dialogWidth: 375px; edge:
Raised; center: Yes; help: No; resizable: No; status: No';

var oParam = new Object();
oParam.confirmButton = 'Yes;
oParam.refuseButton = 'No';
oParam.question = 'Do you want to delete';
return window.showModalDialog("<%=
componentRequest.getWebResourcePath() %>/html/confirm.html", oParam,
sFeatures);

confirm.html:
var oParam = window.dialogArguments;
var sQuestion = oParam.question;
var sConfirmButton = oParam.confirmButton;
var sRefuseButton = oParam.refuseButton;