Error using ERXInQualifier

Hello all

I'm getting the error "qualifierMigratedFromEntityRelationshipPath is 
not supported for qualifier classes of type: ERXInQualifier" when I use 
a fetch specification and set it to deep = false. This entity has 
another one derived, an if I don't do setIsDeep( false ) everything 
works well.
This same error arise when I use another qualifier of my own, 
EOIsInQualifier, so I guess that the problem is in how the qualifiers 
are constructed and how they interact when a inheritance tree is 
involved, but I don't know too much about the EOF innards to know what's 
going on.
Any help would be very appreciated. Thanks.

Santi.