Problem with datatypes

[JensAttermeyer]

I have a Problem with a storedprocedure and datatype conversion. If have the following storedprocedure:

ALTER PROCEDURE [dbo].[spGoodsMovement02]
@IDbName sysname
AS
DECLARE @text nvarchar(max)
IF EXISTS(SELECT * FROM sys.databases where name = @IDbName)
BEGIN
SET @text = N'SELECT TOP 1000
CAST(CONVERT(nchar, lb.Datum, 104) AS DATETIME) AS dateMovement,
lb.products_id AS productId,
lb.products_model AS productsModel,
lb.products_ean AS productsEan,
lb.orders_id AS ordersId,
o.ID AS orderID,
SUM(lb.Bewegung) AS movement,
AVG(lb.Bestand) AS stock,
pd.products_name AS productsName
FROM [' + @IDbName + '].[dbo].[Lager_Bewegungen] AS lb
INNER JOIN [' + @IDbName + '].[dbo].[Products_Description] AS pd ON lb.products_id = pd.products_id
LEFT OUTER JOIN [' + @IDbName + '].[dbo].[Orders] AS o ON o.orders_id = lb.orders_id
WHERE (lb.orders_id > 0)
GROUP BY CAST(CONVERT(nchar, lb.Datum, 104) AS DATETIME), lb.products_id, lb.products_model, lb.products_ean, pd.products_name, lb.orders_id, o.ID
HAVING (SUM(lb.Bewegung) <> 0)
ORDER BY dateMovement DESC,2,3,4,5,6,7'
EXEC (@text) END
PRINT 'NO DATABASE EXISTS'

If I call this storedprocedure in SQL Server Management Studio with a correct parameter for IDbName everything is ok and i get a result. If i call the procedure from my meteor app with Sql.sp() and the correct parameters i get the following error:
"The conversion of a nvarchar data type to a datetime data type resulted in an out-of-range value."
Has anybody an idee what is wrong?