Class cast exception with Fetch Spec

Hello all

I'm getting a Class Cast Exception when trying to execute a fetch 
specification. The code is this:

//===== Code

EOQualifier qual = EOQualifier.qualifierWithQualifierFormat
( "clasificaciones contains %@", new NSArray
( matrizCl.objectAtIndex(0) ) );
EOFetchSpecification fsPrg = new EOFetchSpecification( "Pregunta", qual, 
null );
matrizParcial = ec.objectsWithFetchSpecification( fsPrg );

//===== End Code

This is the last version but I have tried with the 'like' and 'equal' 
operators, the EOToManyQualifier and EOKeyValueQualifier with no avail. 
The key 'clasificaciones' is a flattened relationship resultant of a 
many-to-many join.

The stack trace is this (only a few lines till my method call):

//===== Stack Trace
java.lang.ClassCastException: com.webobjects.foundation.NSArray
[2002-09-26 13:27:07 CEST] <WorkerThread6> java.lang.ClassCastException: 
com.webobjects.foundation.NSArray
	at 
com.webobjects.foundation.NSArray._mutableComponentsSeparatedByString
(NSArray.java:1107)
	at 
com.webobjects.eoaccess.EOSQLExpression.sqlStringForSchemaObjectName
(EOSQLExpression.java:1604)
	at 
com.webobjects.eoaccess.EOSQLExpression._aliasForRelatedAttributeRelationshipPath(
EOSQLExpression.java:233)
	at 
com.webobjects.eoaccess.EOSQLExpression.joinExpression(EOSQLExpression.java:
1000)
	at 
com.webobjects.eoaccess.EOSQLExpression.prepareSelectExpressionWithAttributes(
EOSQLExpression.java:882)
	at 
com.webobjects.jdbcadaptor.JDBCExpression.prepareSelectExpressionWithAttributes(
JDBCExpression.java:266)
	at 
com.webobjects.eoaccess.EOSQLExpressionFactory.selectStatementForAttributes(
EOSQLExpressionFactory.java:189)
	at 
com.webobjects.jdbcadaptor.JDBCChannel.selectAttributes(JDBCChannel.java:191)
	at 
com.webobjects.eoaccess.EODatabaseChannel._selectWithFetchSpecificationEditingContext(
EODatabaseChannel.java:886)
	at 
com.webobjects.eoaccess.EODatabaseChannel.selectObjectsWithFetchSpecification(
EODatabaseChannel.java:218)
	at 
com.webobjects.eoaccess.EODatabaseContext._objectsWithFetchSpecificationEditingContext(
EODatabaseContext.java:3007)
	at 
com.webobjects.eoaccess.EODatabaseContext.objectsWithFetchSpecification
(EODatabaseContext.java:3148)
	at 
com.webobjects.eocontrol.EOObjectStoreCoordinator.objectsWithFetchSpecification(
EOObjectStoreCoordinator.java:452)
	at 
com.webobjects.eocontrol.EOEditingContext.objectsWithFetchSpecification
(EOEditingContext.java:3347)
	at 
com.webobjects.eocontrol.EOEditingContext.objectsWithFetchSpecification
(EOEditingContext.java:3668)
	at WICOPreguntas.buscarPreguntasFiltradas(WICOPreguntas.java:54)
......

//=======

I've searched through the archives for this exception but I didn't find 
anything. Perhaps I didn't look for the right words but, anyway, could 
anybody give me a hint?

I tried to debug the jdbc adaptor also, but setting the 
EOAdaptorDebugEnabled didn't give me any information. The exception is 
thrown before any log. Is there any other place where I could look up 
for debug information?

Thanks a lot. Santi.