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Hi Sergey,
>Sorry, but I got here a return value of -1.6085E+9!!!!

Sorry, try this

create cursor curTest (cKey c(4) nocptrans, iKey i)
insert into curTest values (BinToC(1),1)
ALTER TABLE curTest ALTER COLUMN cKey M NOCPTRANS
lcXml=''
CursorToXML('curTest','lcXml',1,0,0,'1')
XMLToCursor(lcXml,'curTest1')
? curTest1.cKey, CToBin(curTest1.cKey), curTest1.iKey

>The cKey value is stored as gAAAAq== in the XML.

The binary data has to be encoded in order to be included in XML. It'll be decoded by XMLTOCURSOR(). I don't know why CURSORTOXML() doesn't encode character/binary field but only memo/binary. It seems like a bug to me.