I updated from JBoss-2.4.3_Tomcat-3.2.3 to JBoss-2.4.4_Tomcat-3.2.3. Everything worked fine under JBoss-2.4.3_Tomcat-3.2.3 but now with the new version I got an exception that javax.sql.* couldn't be found.
I finally moved 'jboss-jdbc_ext.jar' from jboss/lib to jboss/lib/ext and restarted the Jboss. Now the package could be found by JBoss.
It looks a little strange to me because the log doesn't report anything that something isn't found. Perhaps it would be a good idea to report all loaded jars. ;-)
My environment variable definition is JBOSS_HOME=C:\java\appl\JBoss-2.4.4_Tomcat-3.2.3\jboss