pooled db connections not being closed

I set maxActive to 10 and started getting errors while testing. The log showed that I was running out of connections, which lead me to believe the connections were not being closed. I could not find a problem in the source code, but as I played around with it I inadvertently created a new problem ... I double closed a connection in DbUserManager.selectUserByName and got errors from DbUserManager.authenticate. Researching this new problem, I found a solution to both: http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examples-howto.html#Random_Connection_Closed_Exceptions.
I'm not sure why this applies, but I no longer have abandoned connections being reclaimed.