We are facing a peculiar problem where for some logins the portal page is not completely loading and finally we are getting "Page cannot be displayed" in Internet Explorer.
Following are the details of our production environment.
Web server : Apache 2.2.3 + mod ssl + mod JK
App server : JBoss 4.0.5 GA
Portal server : Jboss Portal 2.4.0
In Apache all the required settings for IE like nokeep alive and downgrading to http 1.0 response etc are configured properly.
After 2 or 3 days if the content of the page changes for that login ID then in the same machine the same portal page is getting displayed properly.
In layouts/index.jsp we have added all the headers to disable caching .