Major Description
The issue is described here: http://www.nabble.com/Unexpected-RuntimeException%3A-RestartResponseException-in-onBeforeRender-of-cached-page-td21683689.html
I also attached a quickstart testcase to the newsgroup entry.
Note regarding the quickstart testcase:
Tthe problem does not show up in the automated test case. It does show up however if you run jetty and then click "TabbedPanels"->"intercept"->"Tabbed Panel".
The difference between the test case and the browser variant seems to be that in the former the AbortException is ultimately (after being rethrown nested in a WicketRuntimeException) caught in the WebRequestCycle.step() method (where a while-loop looks for the cause until it finds the AbortException). In the latter variant the AbortException is caught (also after being rethrown nested in a WicketRuntimeException) in the WebRequestCycle.redirectTo() method where the test of instanceof AbortException fails because the outer exception is a WicketRuntimeException.