Is certainly the redirect problem (under Mozilla)
It happens systematically with jetty. I couldn't reproduce it on tomcat. 

the reason:
          <!-- other steps: add job (redirect to page) -->
          <map:generate src="cocoon://scheduler/publication/{../1}"/>
          <map:transform src="xslt/util/redirect.xsl">
            <map:parameter name="url" value="{request-param:referer}"/>
          </map:transform>
          <map:serialize/>

the scheduler servlet relies on the side effect of getting called through the
internal cocoon pipeline to store a new job. changing the above to

              <map:redirect-to session="true" uri="{request-param:referer}"/>
gets rid of the browser problem but breaks adding jobs.