Did you check the scope of the configured driver on your local WebSphere installation? Maybe an environment variable is still set to use the old version of the driver?
i.e. {ORACLE_JDBC_DRIVER_PATH}/ojdbc.jar
needs to be changed to:
{ORACLE_JDBC_DRIVER_PATH}/ojdbc6.jar
Check for your own version of the driver (5,6,7,8)