There is problem with version definition in Manifest file for servlet-api-2.5.jar
File is located in two different places, in one jar version is defined, in second not. I think these files should be the same.

jboss-eap-5.1/resteasy/embedded-lib/servlet-api-2.5.jar — 2.5
eap51-tattletale/jboss-eap-5.1/resteasy/lib/servlet-api-2.5.jar — Not listed

For details see:
http://hudson.qa.jboss.com/hudson/view/EAP5/job/eap51-tattletale/javadoc/eliminatejars/index.html