[bdbxml] problem with XML file validation

Hi,

i need help about xml validation:

Language used for programming: C#
API used for accessing to DBXML: Parthenon API last version

when i insert a xml file into db, and the validation is disabled, the query 
works correctly; if enable the validation, an exception is thrown:

Sleepycat.DbXml.DbXmlException: Error: XML Indexer: Fatal Parse error in 
document at line, 3, char 240. 
Parser message: An exception occurred! Type:RuntimeException, Message:Could 
not open external entity '{0}', exception code = INDEXER_PARSER_ERROR
at Sleepycat.DbXml.Internal.DbXmlExceptionThrower.ThrowXmlException(Int32 
code, String message)
at Sleepycat.DbXml.Internal.DbXmlPINVOKE.XmlContainer_putDocument__SWIG_3(IntPtr
jarg1, IntPtr jarg2, String jarg3, IntPtr jarg4, IntPtr jarg5, UInt32 jarg6)
at Sleepycat.DbXml.Container.PutDocument(Transaction txn, String name, 
InputStream input, UpdateContext context, DocumentConfig config)
at main.TestCreazioneDb.insertDocument(String nomeFile, String alias) etc 
etc...

does someone know the reason of this mistake?

I thank you in advance.
best regards Luigi Gigliotti