How to get Groups for a User?

Hi,

I need to retrieve User Groups that a user belongs to. I''ll use the groups to lookup the authorization rights for the user.

I'm trying the following:

     String domain = "MYDOMAIN";

     String searchStr = "";

     String belongsToGroup = null;

     String belongsToUser = "testuser";

     Boolean exactMatch = true;

     Boolean findUsers = false;

     Boolean findGroups = true;

     UserSearchResult[]  res = service.retrieveUserGroups(sic.getUserDirectory(),

          domain, searchStr, belongsToGroup, belongsToUser,

          exactMatch, findUsers, findGroups);

However, I'm getting the error:

AxisFault

faultCode: ServerFaultCode

faultSubcode:

faultString: The operation is not supported on the object.

faultActor:

faultNode:

faultDetail:

     NotSupportedFault:null

The retrieveUserGroups() works fine, unless I'm trying to specify the 'belongsToUser' variable.

When using MOB, I'm getting:

Method Invocation Result: NotSupported

Is using the retrieveUserGroups() function the correct way to get the user groups?

What is the reason for the error?