Sp_xml_preparedocument CDATA Reserved Characters

I have tried both in sql server 2000 and sql server 2005 the following code:

DECLARE @DOC VARCHAR(100)
DECLARE @HDOC INT
SET @Doc='<datos><texto><![CDATA[línea átona]]></texto></datos>'
EXEC sp_xml_preparedocument @HDOC OUTPUT, @DOC
SELECT * FROM OPENXML(@HDOC,'datos',2) WITH (texto nvarchar(50))

I always get an error 6603 in SQL2000 and 6602+8179 in SQL2005, wich means it can't parse the 'í' and 'á' characters, though they are in a CDATA.
I have tried with <,>,@ characters and it works fine.

I have also tried using '&aacute;' and '&iacute;' without CDATA but I get the same message:

DECLARE @DOC VARCHAR(100)
DECLARE @HDOC INT
SET @Doc='<datos><texto><l&iacute;nea &aacute;tona></texto></datos>'
EXEC sp_xml_preparedocument @HDOC OUTPUT, @DOC
SELECT * FROM OPENXML(@HDOC,'datos',2) WITH (texto nvarchar(50))