Sorry for double post http://www.jboss.com/index.html?module=bb&op=viewtopic&t=138095,
but there nobody answer me

I have button on my form:

<a4j:commandButton actionListener="#{processDataChangeFioV01.addParagraph}" value="Add Paragraph" reRender="masterFormId:paragraphs">
 <f:param name="destination" value="#{document.content.body}"/>
</a4j:commandButton>

During rendering page with this button, i'm getting exception:

javax.faces.FacesException: Error in conversion Java Object to JavaScript
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:133)
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:98)
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:98)
 at org.ajax4jsf.javascript.JSFunction.appendScript(JSFunction.java:84)
 at org.ajax4jsf.renderkit.AjaxRendererUtils.buildOnEvent(AjaxRendererUtils.java:183)
 at org.ajax4jsf.renderkit.AjaxRendererUtils.buildOnClick(AjaxRendererUtils.java:140)
 at org.ajax4jsf.renderkit.AjaxCommandRendererBase.getOnClick(AjaxCommandRendererBase.java:63)
 at org.ajax4jsf.renderkit.html.CommandButtonRenderer.doEncodeEnd(CommandButtonRenderer.java:114)
 at org.ajax4jsf.renderkit.html.CommandButtonRenderer.doEncodeEnd(CommandButtonRenderer.java:161)
 at org.ajax4jsf.renderkit.RendererBase.encodeEnd(RendererBase.java:135)
 at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:836)
 at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:286)
 at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:262)
 at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:199)
 at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:194)
 at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:121)
 at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:812)
 at javax.faces.component.UIComponent.encodeAll(UIComponent.java:886)
 at javax.faces.render.Renderer.encodeChildren(Renderer.java:137)
 at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:812)
 at javax.faces.component.UIComponent.encodeAll(UIComponent.java:886)
 at javax.faces.component.UIComponent.encodeAll(UIComponent.java:892)
 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:216)
 at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:106)
 at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:251)
 at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:144)
 at javax.faces.webapp.FacesServlet.service(FacesServlet.java:245)
 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$FilterChainImpl.doFilter(SeamFilter.java:83)
 at org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:85)
 at org.jboss.seam.servlet.SeamFilter$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:141)
 at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:281)
 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.debug.hot.HotDeployFilter.doFilter(HotDeployFilter.java:68)
 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:230)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
 at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)

 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:432)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
 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:157)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
 at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:437)
 at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:366)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
 at java.lang.Thread.run(Thread.java:619)
Caused by: javax.faces.FacesException: Error in conversion Java Object to JavaScript
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:133)
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:128)
 ... 65 more
Caused by: java.lang.NoSuchMethodException: Property 'embedable' has no getter method
 at org.apache.commons.beanutils.PropertyUtilsBean.getSimpleProperty(PropertyUtilsBean.java:1127)
 at org.apache.commons.beanutils.PropertyUtilsBean.getNestedProperty(PropertyUtilsBean.java:686)
 at org.apache.commons.beanutils.PropertyUtilsBean.getProperty(PropertyUtilsBean.java:715)
 at org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.java:290)
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:128)
 ... 66 more

As I understand the problem with serializing my #{document.content.body} object to JavaScript.

java.lang.NoSuchMethodException: Property 'embedable' has no getter method

this points that serializer cann't invoke getEmbedable() method for Body object, but this property is Boolean, so it has isEmbedable() method instead of getEmbedable().
So, I think the problem in A4J core: it cann't serialize is-methods.

P.S. If I change <a4j:commandButton/> to <h:commandButton/>
or passing List object as parameter, exception doesn't occure