I have a 2 queries. One takes 45 seconds and the other is instand. The only differences is that the first query has no order. The order by clause uses a primary key. I think that the DATEADD() function is causing the problem. If I don't use the dateadd fuction and hardcode the date, it's much faster as well.

declare @dateonly as datetime

select @dateonly = DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0))

-- query takes 45 seconds
select top 1 somedte, * from sqlservertable
where somedte> @dateonly

-- query is instant
select top 1 somedte, * from sqlservertable
where somedte > @dateonly
order by serialnum desc

Thanks,
Dan