Why It Takes Forever To Execute Stored Procedure In Reporting Services?

I used a stored procedure in my report. If I run the sp in Management Studio (on my pc, database is on a sql server) it takes only several minutes; but from reporting services (also on pc) I put it in the data tab and execute it, it takes forever, actually never finish. I want to know why it's taking so long to execute it from reporting services while it returns data instantly from Mgt Studio. There is cursor in the sp. I don't know whether this is the culprit. Anyone knows why? Thanks!

Below is the sp.
--------------------------------------------------------------------

create proc [dbo].[p_national_by_week]

as

set nocount on



declare @s1 nvarchar(2000), @parmdefinition nvarchar(300), @rangestart smalldatetime, @rangeend smalldatetime

, @price_low money, @price_high money, @weekdate smalldatetime


declare c1 cursor for

--- GG change for reg dates.

select weekdate from vtRealEstate_RealtorListing_WeekDates

open c1

fetch from c1 into @weekdate



while @@fetch_status =0

begin

select @rangeend = @weekdate+7, @rangestart=@weekdate

select @s1 = N'

declare @mlsid_count int, @avg_price money, @avg_day_on_market int, @median_price money, @c1 int

select @mlsid_count=count(*), @avg_price=avg(CurrentPricefilter),

@avg_day_on_market=avg(datediff(dd, FirstListedDate, LastModifiedDate))

from vtRealEstate_RealtorListings

where ((FirstListedDate <= @rangeStart and LastModifiedDate >= @rangeStart) or

(FirstListedDate >= @rangeStart and FirstListedDate < @rangeEnd)

)

and currentpricefilter is not null

and mlsidfilter is not null

select @c1=@mlsid_count/2

set rowcount @c1

select @median_price = CurrentPricefilter from vtRealEstate_RealtorListings

where

((FirstListedDate <= @rangeStart and LastModifiedDate >= @rangeStart) or

(FirstListedDate >= @rangeStart and FirstListedDate < @rangeEnd)

)

and currentpricefilter is not null

and mlsidfilter is not null

order by currentpricefilter

insert report_detail_test (weekdate, mlsid_count, avg_price, median_price

, avg_day_on_market)

values(@weekdate, @mlsid_count, @avg_price, @median_price, @avg_day_on_market)

', @parmdefinition=N'@rangestart smalldatetime, @rangeend smalldatetime, @weekdate smalldatetime'



exec sp_executesql @s1, @parmdefinition, @rangestart=@rangestart, @rangeend=@rangeend

, @weekdate = @weekdate
fetch from c1 into @weekdate

end

select weekdate

, mlsid_count

, avg_price

, median_price

, avg_day_on_market

from report_detail_test

order by WeekDate