5_x build failure is listed here http://hudson.qa.jboss.com/hudson/view/JBoss%20AS/job/JBoss-AS-5.x-sun16/862/console

Possible reasons for missing this error before checkin are:

1. Not doing a clean AS build (cd build;./build.sh clean;./build.sh)

2. Sometimes you need to cleanout thirdparty (assuming no changes have been made to thirdparty/pom.xml):
cd thirdparty; rm -rf *; svn update pom.xml
build AS again