OPEN - issue MNG-2503: mvn.bat file is not correct for 4NT 5.0 and does "endlocal" twice if error http://jira.codehaus.org/browse/MNG-2503 Applying the patch, even though it's not a patch...I was able to generate one using the supplied file and the current mvn.bat file from the trunk.
maven/components/trunk/maven-embedder/src/bin/mvn.bat