TJwString = UnicodeString WideString;
TJwString defines an unicode string type if compiler directive UNICODE is defined; otherwise ansicode Delphi 2009 uses the more efficient UnicodeString type.
However this type must not be used for COM Methods! A cast to WideString is necessary before!
If you get an error here for <= Delphi2007 you must make sure that you're using an updated version of jedi.inc (included by jwscl.inc) that supports the DELPHI2009_UP switch!