Failed To Convert Parameter Value From A String To A Datetime

Hi I am having this problem. I have created a stored proc that uses dynamic sql. Now this works fine when I use it in Query Analyzer.

Now when I try to use this in Reporting services it gives me the error:
'
Failed to generate fields for the query
Check the query syntax or click refresh on query toolbar.
Failed to convert parameter value from a string to a datetime
'

My sotred proc is as:

<quote>
-------------------------------------------------------------------------------------------------------------------------------------

CREATE PROCEDURE [dbo].[rptDetailedAuditsIssued]

(

@param1 varchar(50) ,

@param2 varchar(50),

@param3 varchar(50),

@param4 datetime ,

@param5 datetime



)

AS

begin

declare @strSQL varchar(500)

set @strSQL = 'SELECT * FROM v_DetailedAuditsIssued WHERE '

if @param1 <> ''

Begin

set @strSQL = @strSQL + 'strRegion = ' + @param1 + ' AND '

End



if @param2 <> ''

Begin

set @strSQL = @strSQL + ' strTaxTypeCode = ' + @param2 + ' AND '

End



if @param3 <> ''

Begin

set @strSQL = @strSQL + ' strAuditType = ' + @param3 + ' AND '

End

set @strSQL = @strSQL + ' (dtmIssuedDate BETWEEN '''

+ CONVERT(nvarchar(30), @param4, 101) + ''' AND '''

+ CONVERT(nvarchar(30),@param5, 101) + ''')'



exec (@strSQ



end
--------------------------------------------------------------------------------------------------------------------------
</quote>

When I run


rptDetailedAuditsIssued '','','','1/1/2000','1/1/2001'in query editor it runs fine. But gives me that error every time I run it in SSRS. I think I got this problem but in earlier cases I used to set the param values to null in Repservices and it worked but its not working this time. This time it stops complaining but does generate any fields.