Hudson hangs performing maven release build with CVS

Executing a release build using maven-release hudson hangs performing CVS
update. Nothing to see in logs, output is always the same:

Started by user shofmann
Baue auf Master
[maven-release-test] $ cvs -Q -z3 -d :ext:<user@cvs.de>:/home/cvsroot co -P -d
workspace -D "Thursday, November 5, 2009 9:36:23 AM UTC" maven-release-test
$ computing changelog
Parsing POMs
[workspace] $ /usr/lib/jvm/java-1.5.0-sun/bin/java -cp
/opt/hudson/plugins/maven-plugin/WEB-INF/lib/maven-agent-1.332.jar:/opt/apache-maven-2.2.0/boot/classworlds-1.1.jar
hudson.maven.agent.Main /opt/apache-maven-2.2.0
/var/run/hudson/war/WEB-INF/lib/remoting-1.332.jar
/opt/hudson/plugins/maven-plugin/WEB-INF/lib/maven-interceptor-1.332.jar 35593
/opt/hudson/plugins/maven-plugin/WEB-INF/lib/maven2.1-interceptor-1.2.jar
<===[HUDSON REMOTING CAPACITY]===>channel started
Executing Maven: -B -f /opt/hudson/jobs/maven-release-test/workspace/pom.xml
-Dresume=false -P integration release:prepare release:perform
[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'release'.
[INFO] ------------------------------------------------------------------------
[INFO] Building maven-release-test
[INFO] task-segment: [release:prepare, release:perform] (aggregator-style)
[INFO] ------------------------------------------------------------------------
[INFO] [release:prepare

]
[INFO] Verifying that there are no local modifications...
[INFO] Executing: /bin/sh -c cd /opt/hudson/jobs/maven-release-test/workspace &&
cvs -z3 -f -d :ext:<user@cvs>:/home/cvsroot -n -q update -d
[INFO] Working directory: /opt/hudson/jobs/maven-release-test/workspace

At CVS server I see that three SSH sessions were opended and closed for hudson
user but fourth session will never be closed... Normal builds work fine.