Datetime format in a query depends on server language

Hello,

I have got a problem with a query in MS SQL Server:

The following query returns a correct number of records (please consider the German datetime format):

SELECT     *
FROM         kontakte_benutzer
WHERE     (datum_von >= '02-09-2004 00:00:00')

The following query returns no records:

SELECT     *
FROM         kontakte_benutzer
WHERE     (datum_von >= '02-09-2004 00:00:00') AND (datum_von <= '02-09-2004 23:59:59')

In case of changing the datetime format I get records again:

SELECT     *
FROM         kontakte_benutzer
WHERE     (datum_von >= '2004-09-02 00:00:00') AND (datum_von <= '2004-09-02 23:59:59')

Because we use an English and a German MS SQL Server, this will be problematic.
Does anybody know how to change the query in order to get records both with a German and an English Server?

Many thanks.