DataSourceUserManager and addToRole

[Armin Michel]

I configured my App to use the DataSourceUserManager. According to 
orionsupport and Orion API I added the following text to my 
orion-application.xml:

<user-manager class="com.evermind.sql.DataSourceUserManager">
       <property name="table" value="users" />
       <property name="usernameField" value="username" />
       <property name="passwordField" value="password" />
       <property name="defaultGroups" value="users" />
       <property name="groupMembershipTableName" value="user_groups" />
       <property name="groupMembershipGroupFieldName" value="groupname" />
       <property name="groupMembershipUsernameFieldName" value="username" />
       <property name="dataSource" value="jdbc/DefaultDS" />
       <property name="staleness" value="1000" />
       <property name="debug" value="true" />
 </user-manager>

In my DBMS I did the following:

create table user_groups (username varcharg, roupname varchar);
create table users (username varchar,password varchar);

Adding a new User with:
        Principal user = roleManager.createPrincipal("userName","password");
works perfectly.

But when I do a: roleManager.addToRole(user,"aRole");
I get the following exception:

java.lang.RuntimeException: SQL error: No value specified for parameter 2.
        at java.lang.RuntimeException.<init>(RuntimeException.java:49)
        at com.evermind.sql.DataSourceUser.addToGroup(JAX)
        at com.evermind.server.hm.addToRole(JAX)

Using the default UserManager I don't get any exception.

Could anyone help me here?