We see this with Embedded Jopr running in a JBAS 5.0 snapshot, which bundles JSF 1.2_10.

Here's the stack trace:

10:25:29,748 ERROR [viewhandler] Error Rendering View[/secure/resourceInstanceConfig.xhtml]
java.lang.ClassCastException: java.lang.String
at javax.faces.component.UISelectBoolean.isSelected(UISelectBoolean.java:106)
at com.sun.faces.renderkit.html_basic.CheckboxRenderer.getEndTextToRender(CheckboxRenderer.java:137)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeEnd(HtmlBasicRenderer.java:160)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:861)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:242)
at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234)
at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837)
at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:282)
at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:262)
at org.richfaces.renderkit.html.SimpleToggleControlTemplate.doEncodeChildren(SimpleToggleControlTemplate.java:347)
at org.richfaces.renderkit.html.SimpleToggleControlTemplate.doEncodeChildren(SimpleToggleControlTemplate.java:342)
at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:121)
at org.richfaces.renderkit.html.SimpleTogglePanelRenderer.encodeChildren(SimpleTogglePanelRenderer.java:208)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:930)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:933)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:148)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:930)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:933)
at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:592)
at org.ajax4jsf.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:108)
at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:196)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83)
at org.jboss.seam.debug.hot.HotDeployFilter.doFilter(HotDeployFilter.java:68)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:85)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:177)
at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:267)
at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:380)
at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:507)
at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:60)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:58)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:190)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:93)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:828)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:601)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:595)