Found following NPE in system log after a configuration failed:

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2010-01-28 08:02:18,5 [10099531@qtp-30216319-1573] ERROR org.apache.wicket.RequestCycle -
    java.lang.NullPointerException
        at com.pmease.quickbuild.web.DefaultCacheManager.getHistoryCount(DefaultCacheManager.java:451)
        at sun.reflect.GeneratedMethodAccessor26.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.apache.wicket.proxy.LazyInitProxyFactory$JdkHandler.invoke(LazyInitProxyFactory.java:416)
        at org.apache.wicket.proxy.$Proxy42.getHistoryCount(Unknown Source)
        at com.pmease.quickbuild.web.page.dashboard.DashboardPage$3.newCell(DashboardPage.java:97)
        at com.pmease.quickbuild.web.component.treetable.TreeTable.newRow(TreeTable.java:409)
        at com.pmease.quickbuild.web.component.treetable.TreeTable.access$6(TreeTable.java:287)
        at com.pmease.quickbuild.web.component.treetable.TreeTable$6.onClick(TreeTable.java:361)
        at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:65)
        at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:163)
        at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:297)
        at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(BehaviorRequestTarget.java:104)
        at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:91)
        at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1239)
        at org.apache.wicket.RequestCycle.step(RequestCycle.java:1316)
        at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1418)
        at org.apache.wicket.RequestCycle.request(RequestCycle.java:532)
        at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:356)
        at org.apache.wicket.protocol.http.WicketServlet.doGet(WicketServlet.java:124)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:596)
        at com.pmease.quickbuild.web.WebServlet.service(WebServlet.java:58)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
        at org.eclipse.equinox.http.servlet.internal.ServletRegistration.handleRequest(ServletRegistration.java:90)
        at org.eclipse.equinox.http.servlet.internal.ProxyServlet.processAlias(ProxyServlet.java:111)
        at org.eclipse.equinox.http.servlet.internal.ProxyServlet.service(ProxyServlet.java:59)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
        at org.eclipse.equinox.http.jetty.internal.HttpServerManager$InternalHttpServiceServlet.service(HttpServerManager.java:318)
        at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:502)
        at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:380)
        at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
        at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
        at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
        at org.mortbay.jetty.Server.handle(Server.java:324)
        at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:535)
        at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:865)
        at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:540)
        at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:213)
        at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
        at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228)
        at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:520)
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