Tomcat logging problem

Hi! I'm getting this message when I start tomcat-5.5.16:
log4j:WARN No appenders could be found for logger (org.apache.catalina.startup.ClassLoaderFactory).
log4j:WARN Please initialize the log4j system properly.

I have already read the tomcat logging guide at http://tomcat.apache.org/tomcat-5.5-doc/logging.html
Still, I am getting the message above. No logs are written to /logs/tomcat.log. The file doesn't even exist! I have already added these lines to my webapp to test logging:
Log log = LogFactory.getLog(this.getClass());
log.debug("this is a test log");

I do not have any other log4j.properties specific to my webapp. only the one in $(catalina_home)/common/classes/log4j.properties. Here it is:
log4j.rootLogger=debug, R
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=${catalina.home}/logs/tomcat.log
log4j.appender.R.MaxFileSize=10MB
log4j.appender.R.MaxBackupIndex=10
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n
log4j.logger.org.apache.catalina=DEBUG, R

I have already googled for this. Nothing helped. I have only gotten more frustrated.
Any help would be appreciated. Thanks!

P.S.
I'm using java 1.5.0_06 with ObjectWeb Lomboz 3.1.2 on windows xp home edition.