Hi Sergey,
Thanks, to pre-convert "true"/"flase" with strtran() really is a skillful idea.
However,as per your hint,i did further try with datetime parameters again,still failed.
is it possibly caused by different SQL environment? mine is SQL2k+SP3.
Testing codes in SQL Query Analyzer:

declare @xl varchar(8000)
select @xl=
'<?xml version = "1.0" encoding="Windows-1252" standalone="yes"?>
<VFPData>
	<tmp>
		<dt>2005-01-24T13:25</dt>
	</tmp>
	<tmp>
		<dt>2005-01-24T13:25</dt>
	</tmp>
	<tmp>
		<dt>2005-01-24T13:26</dt>
	</tmp>
	<tmp>
		<dt>2005-01-24T13:35</dt>
	</tmp>
	<tmp>
		<dt>2005-03-05T00:00</dt>
	</tmp>
	<tmp>
		<dt>2005-02-03T00:00</dt>
	</tmp>
	<tmp>
		<dt>2005-01-25T00:00</dt>
	</tmp>
</VFPData>
'
--Note that the XML script was generated with cursortoxml() in VFP9.  
exec ReadXML @xl

SP - ReadXML:

CREATE PROCEDURE  ReadXML 
(
@xml  Varchar(8000)
)
as
declare @xdoc int
exec sp_xml_preparedocument @xdoc output, @xml 
select t.* from openxml (@xdoc, '/VFPData/tmp', 2)   with ( dt datetime)  as t
exec sp_xml_removedocument @xdoc
GO

Error message raised in SQL Query Analyzer:

Server: Msg 241, Level 16, State 1, Procedure ReadXML, Line 8
Syntax error converting datetime from character string.