What does it mean or what is the reason for this Error?

13:57:03,078 INFO  - [echo] Starte: com.xyz.javamain 
13:59:07,743 INFO  - Terminating launched command gracefully...
13:59:07,862 INFO  - Killing process 5396 and all its descendant processes...
13:59:09,074 INFO  - Executing post-execute action...
13:59:09,075 ERROR - Step 'master>Build-Ant' is failed.
    java.lang.RuntimeException: java.lang.InterruptedException 
        at com.pmease.quickbuild.execution.Commandline.execute(Commandline.java:375) 
        at com.pmease.quickbuild.execution.Commandline.execute(Commandline.java:223) 
        at com.pmease.quickbuild.plugin.builder.ant.AntBuildStep.run(AntBuildStep.java:288)

I get this message more often now on our test system.

The error above, for example, comes from an Ant java task

<java classname="com.xyz.javamain"  classpathref="Class.Path" fork="true"  dir="${WorkDir}" logError="true"
      failonerror="false" error="Error.log" jvm="jdk8/x64/windows/bin/java.exe" output="Output.log" classpath="${ProjectClassPath}">
      <jvmarg value="-Xmx512m"/>
</java>

Georg