Tomcat Pool Empty - spring

Question

We are using Tomcat 6 with tomcat-jdbc.jar and tomcat pooling (we are currently using the latest version 7.0.28, but have tried with previous versions as well).
This is using PostgreSQL on the back-end.
About once every 2 - 5 days (it's rather "random" in happening), our server uses up all of the available db connections, in about a 10 minute period, and we see these in the logs (we've turned on FINE logging):
2012-10-01 18:40:29,998 ERROR [TP-Processor29] JDBCExceptionReporter.logExceptions(72) | [TP-Processor29] Timeout: Pool empty. Unable to fetch a connection in 0 seconds, none available[size:150; busy:41; idle:0; lastwait:0].
2012-10-01 18:40:30,000 ERROR [TP-Processor29] JDBCExceptionReporter.logExceptions(72) | [TP-Processor29] Timeout: Pool empty. Unable to fetch a connection in 0 seconds, none available[size:150; busy:41; idle:0; lastwait:0].
I'm trying to track down the root cause problem of this.
When looking at the db and this occurs, all of the connections are shown as "IDLE".
Our current configuration looks something like this:
<bean id="dataSource" class="org.apache.tomcat.jdbc.pool.DataSource" destroy-method="close">
<property name="driverClassName" value="org.postgresql.Driver"/>
<property name="url" value="jdbc:postgresql://db/dbname?useUnicode=true&characterEncoding=utf-8"/>
<property name="username" value="postgres"/>
<property name="password" value="postgres"/>
<property name="initialSize" value="8"/>
<property name="maxActive" value="150"/>
<property name="maxIdle" value="10"/>
<property name="maxWait" value="30"/>
<property name="defaultAutoCommit" value="true"/>
<property name="validationQuery" value="SELECT 1"/>
<property name="validationInterval" value="60000"/>
</bean>
And, our logging in logging.properties is:
org.apache.tomcat.jdbc.pool.level=FINE
Most of the time, we are using about 15 - 20 database connections, however, as I mentioned, the problem is that every few days, it rapidly uses up all of the connections, and requires a restart.
We're trying to track this down to being a Tomcat pool issue, a Hibernate issue, a Spring issue, or an app issue.
To start with, any ideas why:
A) Why does it show: [size:150; busy:41; idle:0; lastwait:0] ... where are the other 150-41 connections?
B) When logging, it shows when the connection opens, but not when it closes. How can we turn that on?