Starting and Stopping

Remove the contents of the tomcat work directory:

/etc/init.d/gsrc stop
rm /usr/local/tomcat/logs/*; rm -rf /usr/local/tomcat/work/Standalone/localhost/*
/etc/init.d/gsrc start

Validating xml files

xmllint -dtdvalid http://java.sun.com/dtd/web-app_2_3.dtd ~/java/gigascale/WEB-INF/web.xml

Logs

There are various logs in /usr/local/tomcat/logs

catalina.out
catalina_log.2008-12-19.txt
andrewsj_log.2008-12-19.txt chessj_log.2008-12-19.txt embeddedj_log.2008-12-19.txt localhost_access_log.2008-12-19.txt localhost_log.2008-12-19.txt trustj_log.2008-12-19.txt
mod_jk.log

/usr/local/apache/conf/tomcat-mod_jk.conf refers to the proper mod_jk.so file and that mod_jk.so is present
One idea is to check that the GSRC java pages needed to be compiled with the same mod_jk.so. However, Working with mod_jk from tomcat-4.0 says
Note: The version of mod_jk is not dependent on the version of Tomcat. The Tomcat 3.3 distribution of mod_jk will function correctly with Tomcat 4.x and other 3.x versions of Tomcat, such as Tomcat 3.2.1.
FWIW: Preparing a Javapages release.

catalina.out

When I update libexec/mod_jk.so with the new version and restart, catalina.out contains:

Stopping service Tomcat-Standalone
mod_jk location: libexec/mod_jk.so
Make sure it is installed corectly or  set the config location
Using 
Starting service Tomcat-Standalone

The "Make sure it is installed corectly" comes from: ApachConfig.java which is trying to write a new configuration file.

It looks like these message appear if one runs /etc/init.d/gsrc start in a directory other than /usr/local/apache - the problem is that libexec/mod_jk.so must exist.

tomcat-3.3 mod_jk howto suggests:

$APACHE_HOME/bin/apachectl configtest

to determine whether to compile with EAPI