I would recommend trying Seam 2.2.0.GA with JBoss 5.x or JBoss 4.2.x.

Compare your web.xml with the ones in the remoting examples of the distro.

Here's the web.xml for the chatroom example:

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <!-- Seam -->
   
    <listener>
        <listener-class>org.jboss.seam.servlet.SeamListener</listener-class>
    </listener>

    <filter>
      <filter-name>Seam Filter</filter-name>
      <filter-class>org.jboss.seam.servlet.SeamFilter</filter-class>
    </filter>
    
    <filter-mapping>
      <filter-name>Seam Filter</filter-name>
      <url-pattern>/*</url-pattern>
    </filter-mapping> 
    
    <servlet>
      <servlet-name>Seam Resource Servlet</servlet-name>
      <servlet-class>org.jboss.seam.servlet.SeamResourceServlet</servlet-class>
    </servlet>
    
    <servlet-mapping>
      <servlet-name>Seam Resource Servlet</servlet-name>
      <url-pattern>/seam/resource/*</url-pattern>
    </servlet-mapping>      

    <context-param>
        <param-name>facelets.DEVELOPMENT</param-name>
        <param-value>true</param-value>
    </context-param>

    <context-param>
        <param-name>javax.faces.DEFAULT_SUFFIX</param-name>
        <param-value>.xhtml</param-value>
    </context-param>

    <!-- Faces Servlet -->
    
    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.seam</url-pattern>
    </servlet-mapping>

</web-app>