I have a trouble
[INFO] Scanning for projects...
[INFO] ----------------------------------------------------------------------------
[INFO] Building Flexess: JCE provider
[INFO] task-segment: [clean, deploy]
[INFO] ----------------------------------------------------------------------------
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from jinternal-sn
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from jopen-sn
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from apache snapshot repository
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from codehaus snapshot repository
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from codehaus-release-repo
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from java.net
[INFO] snapshot org.apache.maven.plugins:maven-jar-plugin:2.2-SNAPSHOT: checking for updates from spring-ext
Downloading: http://people.apache.org/repo/m2-snapshot-repository/org/apache/maven/plugins/maven-jar-plugin/2.2-SNAPSHOT/maven-jar-plugin-2.2-20071207.230654-4.pom
7K downloaded
Downloading: http://people.apache.org/repo/m2-snapshot-repository/org/apache/maven/plugins/maven-jar-plugin/2.2-SNAPSHOT/maven-jar-plugin-2.2-20071207.230654-4.jar
25K downloaded
[INFO] [clean:clean]
[INFO] Deleting directory /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target
[INFO] Deleting directory /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/classes
[INFO] Deleting directory /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/test-classes
[INFO] Deleting file-set: /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/bin (included: [], excluded: [])
[INFO] Preparing source:jar
[WARNING] Removing: jar from forked lifecycle, to prevent recursive invocation.
[INFO] [org.jresearch.commons.obfuscate.:check {execution: default}]
[INFO] Skip the obfuscating activity for the project com.jresearchsoft.uam.license:com.jresearchsoft.uam.license.provider:1.0.0-SNAPSHOT - disable
[INFO] [source:jar {execution: attach-sources}]
[INFO] Building jar: /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/com.jresearchsoft.uam.license.provider-1.0.0-SNAPSHOT-sources.jar
[INFO] [org.jresearch.commons.obfuscate.:check {execution: default}]
[INFO] Skip the obfuscating activity for the project com.jresearchsoft.uam.license:com.jresearchsoft.uam.license.provider:1.0.0-SNAPSHOT - disable
[INFO] [resources:resources]
[INFO] Using default encoding to copy filtered resources.
[INFO] [compiler:compile]
Compiling 10 source files to /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/classes
[INFO] [resources:testResources]
[INFO] Using default encoding to copy filtered resources.
[INFO] [compiler:testCompile]
Compiling 4 source files to /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/test-classes
[INFO] [surefire:test]
[INFO] Tests are skipped.
Downloading: http://server.jresearch.org:28080/internal-snapshot//org/apache/maven/plugins/maven-jar-plugin/2.2-SNAPSHOT/maven-jar-plugin-2.2-20071207.230654-4.pom
Downloading: http://www.jresearch.org/open-snapshot/org/apache/maven/plugins/maven-jar-plugin/2.2-SNAPSHOT/maven-jar-plugin-2.2-20071207.230654-4.pom
Downloading: http://people.apache.org/repo/m2-snapshot-repository/org/apache/maven/plugins/maven-jar-plugin/2.2-SNAPSHOT/maven-jar-plugin-2.2-20071207.230654-4.pom
7K downloaded
[INFO] [jar:jar]
[INFO] Building jar: /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/com.jresearchsoft.uam.license.provider-1.0.0-SNAPSHOT.jar
[INFO] [jar:sign {execution: default}]
[debug] jarsigner executable=[/usr/jdk/instances/jdk1.5.0/jre/../bin/jarsigner]
[debug] Executing: /bin/sh -c 'cd /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider && /usr/jdk/instances/jdk1.5.0/jre/../bin/jarsigner -verify -verbose "/var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/com.jresearchsoft.uam.license.provider-1.0.0-SNAPSHOT.jar"'
[warn] /bin/sh: /var/data/maven/hudson/jobs/Jresearch: does not exist
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Result of /bin/sh -c 'cd /var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider && /usr/jdk/instances/jdk1.5.0/jre/../bin/jarsigner -verify -verbose "/var/data/maven/hudson/jobs/Jresearch Flexess/workspace/new_root/general/1.0.0/../../license/trunk/pom/../provider/target/com.jresearchsoft.uam.license.provider-1.0.0-SNAPSHOT.jar"' execution is: '1'.
[INFO] ------------------------------------------------------------------------
[INFO] For more information, run Maven with the -e switch
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 31 seconds
[INFO] Finished at: Sun Dec 09 17:54:44 CET 2007
[INFO] Final Memory: 11M/26M
[INFO] ------------------------------------------------------------------------
Looking at the plexus code, I believe the problem may be fixed by forcing the upgrade to plexus >= 1.2 (where the shell element was introduced).
Could you try building a local maven-jar-plugin that reuses the latest plexus and see if that fixes your issue ?