The ace:accordion when used with the 'panechange' event of the ace:ajax component - does not register events in the same way as it does when used with the paneChangeListener attribute enabled. This happens in all browsers when either the dynamic or the collapsible attributes of the ace:accordion is set to true.

If dynamic=true, when accordion changes panes, the ajax paneChange event is not received. This is different for an accordion with a paneChangeListener, that will always receive a pane change event, also when dynamic=true.

If collapsible=true, when collapsing the accordion's open pane followed by its re-opening, an accordion with an ace:ajax component using its paneChange event will receive 2 events, while an accordion with a paneChangeListener will register only one event.

This can be reproduced with the accordion test application located at:
http://server.ice:8888/svn/repo/qa/trunk/Regression-Icefaces2/Sparkle/Nightly/accordion
- load the attribute page: http://localhost:8080/accordion/accordionAttribute.jsf
- change accordion panes and notice the AjaxBehaviorEvent messages with dynamic attribute unchecked, then with dynamic attribute enabled.
- enable collapsible=true and notice the AjaxBehaviorEvent messages.