Trigger not launched from interface

Question

Hello:

I have a table with an after update trigger in SQL 2005. If I update directly with SQL QUERY the trigger runs ok.

This table is connected using a dataset and tableadapter to a DXDBGrid (Dev. Express).

If the user updates the grid, the underlying data is updated, but the trigger is not launched.

I've a PK on table, auto-generated UPDATE command in the table adapter, etc. Everything works fine except the trigger not launching...

Why, oh why!?

Thanks in advance.

Franklin.

EDIT: The trigger code:

ALTER TRIGGER [dbo].[trgUpdateZonasAsignadas] ON [dbo].[ZonasAsignadas] AFTER UPDATE AS BEGIN

IF NOT(UPDATE(ActualizadoPDA))
BEGIN
   UPDATE ZonasAsignadas SET ActualizadoPDA=0
      WHERE IdUsuarioZona IN (SELECT Inserted.IdUsuarioZona FROM Inserted)   
END

END