I have the same problem. Did you manage to find a solution for this? I have a modal panel which is more expensive to render than the main page but will probably be opened by users very rarely so it would be best to load its content on demand.
I tried to use a4j:include to make something like a wizzard as described here: http://livedemo.exadel.com/richfaces-demo/richfaces/include.jsf?c=include, but with a modalPanel
The original content of the wizzard is something easy to render like a simple "Loading..." and when the modalPanel is shown I automatically change its view to the real content. Everything works very well and as desired but not in Internet Explorer where the real content at the second page is now shown. This behaviour is described in this jira: https://issues.jboss.org/browse/RF-2505
Is there a way I can achive the above for all browsers?