There appears to be an invalid tld file in that deployment:
Caused by: org.xml.sax.SAXException: cvc-complex-type.2.4.a: Invalid content was found starting with element 'description'. One of '{"http://java.sun.com/xml/ns/javaee":type, "http://java.sun.com/xml/ns/javaee":deferred-value, "http://java.sun.com/xml/ns/javaee":deferred-method}' is expected. @ vfs:///C:/JBoss/jboss-as-distribution-6.0.0.20101110-CR1/jboss-6.0.0.20101110-CR1/server/default/deploy/MySeam.war/WEB-INF/lib/jboss-seam-ui.jar/META-INF/s.tld[2444,18]
See this http://community.jboss.org/message/566054