While attempting to transfer data from Salesforce using Apex Data Loader to Oracle Keep getting the following error:

    26937 [databaseAccountExtract] FATAL com.salesforce.dataloader.dao.database.Data
baseContext  - Error getting value for SQL parameter: nkey__c.  Please make sure
 that the value exists in the configuration file or is passed in.  Database conf
iguration: insertAccount.

The database-conf.xml has the following beans:

<bean id="insertAccount"
      class="com.salesforce.dataloader.dao.database.DatabaseConfig"
      singleton="true">
    <property name="sqlConfig" ref="insertAccountSql"/>
    <property name="dataSource" ref="dbDataSource"/>
</bean>
<bean id="insertAccountSql" class="com.salesforce.dataloader.dao.database.SqlConfig" singleton="true">
    <property name="sqlString">
        <value>
            INSERT INTO VANTROPO.SF_ACCOUNTCHANNEL (nkey__c)
            VALUES (@nkey__c@)
        </value>
    </property>
    <property name="sqlParams">
        <map>
   <entry key="nkey__c" value="java.lang.String"/>
        </map>
    </property>
</bean>

The SDL (mapping file) has the following values:

# Account Insert Mapping values for query from Salesforce (left) and insert/update to Oracle (right)
# SalesforceFieldName=OracleFieldName
nkey__c=NKEY__C

Any help appreciated.