The date popup of rich:calendar is not visible if use in rich:tabPanel.
Problem comes in IE8 everything is fine in FF3
I am using richfaces verssion 3.3.3.
http://livedemo.exadel.com/richfaces-demo/richfaces/calendar.jsf there the calendar lies in tabPanel (as all the examples does.) So please add more details. And make sure it's not caused by some application CSS using firebug.