Problem with Commons Logging / Log4j setup in spring webapp with tomcat 6

I have a problem wih a logging setup in a apring webapp deployed under tomcat 6.

The webapp uses the commons-logging api, on runtime log4j should be used. The log file is created but remains empty - no log entries occur.

the setup is the following:

WEB-INF/web.xml:

 <context-param>
    <param-name>log4jConfigLocation</param-name>
    <param-value>/WEB-INF/log4j.xml</param-value>
  </context-param>
  <listener>
    <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
  </listener>

WEB-INF/classes/commons-logging.properties:

org.apache.commons.logging.Log=org.apache.commons.logging.impl.Log4JLogger

WEB-INF/log4j.xml:

<log4j:configuration xmlns:log4j='http://jakarta.apache.org/log4j/'>

  <appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
    ...
  </appender>
  <appender name="FILE" class="org.apache.log4j.RollingFileAppender">
    <param name="File" value="${catalina.home}/logs/my.log"/>
    ...
  </appender>

  <logger name="my.package">
    <level value="INFO"/>
  </logger>

  <root>
    <level value="ERROR"/>
    <appender-ref ref="CONSOLE"/>
    <appender-ref ref="FILE"/>
  </root>
</log4j:configuration>

The file logs/my.log is created, but no logs appear. The are info logs on the tomcat console, but not with the layout pattern configured.

The commons-logging-1.1.1.jar and log4j-1.2.14.jar are included in WEB-INF/lib. Any idea what is wrong here?