Java JNDI in Tomcat: BeanCreationException / NamingException on global Resource. Looking for the same class that global resource returns

I don't understand what can cause a Bean creation exception on behalf to return the same class as required.

The class is com.mchange.v2.c3p0.ComboPooledDataSource, and the error says that was expected to return an instance of [com.mchange.v2.c3p0.ComboPooledDataSource] but returned an instance of [com.mchange.v2.c3p0.ComboPooledDataSource]

This is the error:

org.springframework.beans.factory.BeanCreationException:
Error creating bean with name 'dataSourceGCA' defined in class path resource [META-INF/xxxxx-security-app.xml]: 
Invocation of init method failed; nested exception is javax.naming.NamingException: 
The local resource link [dataSourceGCA2] that refers to global resource [jdbc/dataSourceGCA2Global] was expected to return an instance of [com.mchange.v2.c3p0.ComboPooledDataSource] but returned an instance of [com.mchange.v2.c3p0.ComboPooledDataSource]

I'm using Java 7 and Tomcat 7.

This is the config of datasource:

In context.xml:

<ResourceLink name="jdbc/dataSourceGCA2"
  global="jdbc/dataSourceGCA2Global"
  auth="Container"
  type="com.mchange.v2.c3p0.ComboPooledDataSource" />

In server.xml:

<Resource description="whatever"
  name="jdbc/dataSourceGCA2Global"
  auth="Container"
  factory="org.apache.naming.factory.BeanFactory"
  type="com.mchange.v2.c3p0.ComboPooledDataSource"
  user="xxxxxxxx"
  password="xxxxxxxx"
  initialPoolSize="1"
  minPoolSize="1"
  maxPoolSize="5"
  acquireIncrement="1"
  driverClass="oracle.jdbc.driver.OracleDriver"
  jdbcUrl="jdbc:oracle:thin:@tprodva2:1522/BD2"
  testConnectionOnCheckin="true"
  idleConnectionTestPeriod="300"
  maxIdleTimeExcessConnections="0"
  maxIdleTime="0" />

What can cause this behaviour?

Any help is appreciated.

Solution

(was gonna comment but I have too little reputation)

This can be caused by the same class being loaded by two different classloaders.