ASP page, stored procedure, dynamic where clause problem

MS SQL Server 2000 (remotely hosted by others)
ASP

Hi, and thank you very much, in advance, for any help you can offer!

I am able to retrieve records from several stored procedures on an ASP page, so there should be no connectivity issues.

But, my big headache is a stored procedure that has a dynamic WHERE clause. In trying to troubleshoot the problem, I have used Response.Write to get an exact copy of the parameter, and I have executed the stored procedure (using MS SQL Server Management Studio), and have pasted that exact phrase as the "Value." It works!

But when I try to run it from the ASP page, I get the following error:
=================================================
Microsoft OLE DB Provider for ODBC Drivers error '80040e07'

[Microsoft][ODBC SQL Server Driver]Invalid character value for cast specification

/RCTSearchResults.asp, line 1143
=================================================

Just for reference, here are lines 1142, and line 1143. 1143 is the .Open(), and that's where it fails:
rsInvItems.Source = "{call dbo.sp7smInvDynSql37(" + strSQLSourceString +  ")}"
rsInvItems.Open ()

I have looked up the error by code and by searching, to no avail. As far as I can tell, there is no "difficult" type casting (like dates) - I'm using only integers (tinyint and smallint integers.) Obviously, sending a string with numbers in the string forces SQL Server to typecast text strings into integers, but remember, the exact same phrase will work as the value parameter when input at the server.

Here's the latest attempt at the dynamic WHERE clause that is the parameter:

strSQLSourceString = ((dbo.tblInv.intInvDisplay = 1) AND (fk_intInvSpecID IN (3)) AND (fk_intInvStatID = 2) ) ORDER BY strItemTypeN, strSpecName, strPatt, fk_intInvStatID DESC, curInvPrice DESC

Note that I am using the "IN" operator, in case that helps to figure this out.

Finally, so anyone willing to help will have everything, here is enough of the stored procedure to give you an idea if anything is wrong. You'll see that I tried both ways to execute, and I have tried declaring the @SQLStatement as both varchar and nvarchar. The stored proc is kind of big, so I snipped out what would probably not be necessary to see for troubleshooting:

=======================================================

ALTER Procedure [dbo].[sp7smInvDynSql37] (@DynSQLString varchar(1000) )

AS

DECLARE @SQLStatement nvarchar(4000)

set @SQLStatement = 'SELECT dbo.tblInv.pk_intInvIID,
    dbo.tblItemType.strItemTypeName,
    dbo.tblSpecies.strSpecName,

   (snip)

    dbo.tblInvItemStatus.strInvItemStatus
FROM dbo.tblInv INNER JOIN
    dbo.tblItemType ON

   (snip)

 WHERE ' + '  ' + @DynSQLString  + ' '
 
-- EXEC sp_executesql @SQLStatement
EXEC (@SQLStatement)

=====================================

Again, thanks for any help you can offer.

Dennis