Cursor Issue - Order Not Correct

I'm using a cursor in SQL Server 2000 to assist me in calculating for each store, the Sales Rank of a zip code. There are about 1500 stores, and 125,000 store/sales/zip code records.

I am finding that this works for about 95% of the stores, but about 5% are getting fouled up, where the store's records are getting split in the sequencing, and so the store ends up with two zips ranked 1, two ranked 2, two ranked 3, etc.

In the DB structure, there is a constraint restricting one record per store (org_id) per zip code (postalcode).

Here's my code. Basically what I'm trying to have the cursor do is go through the table, ordered by org_id (store) asc, org_criteria_value (sales) desc, and rank the zip codes. When a new store is encountered, reset the counter to 1 and start ranking again. Do this until all the records are processed.

/*CREATE Sales_Table table */
CREATE TABLE [dbo].[Sales_Table] (
[count_id] [int] NULL ,
[org_id] [int] NULL ,
[postalcode] [varchar] (20) NULL,
[sales] [numeric](18,6) NULL ,
[sales_rank] [integer] NULL,
[org_criteria_input_date] [datetime] NULL
) ON [PRIMARY]


insert into Sales_Table
select 0 as count_id, omd.org_id, omd.postalcode, omd.org_criteria_value, 0 as cum_rank, org_criteria_input_date
fromorg_model_data omd
join org o on o.org_id = omd.org_id
where o.client_id = @ClientID
and model_Criteria_id = 27
and org_criteria_value <> 0
order by omd.org_id asc, omd.org_criteria_value desc


-- DECLARE CURSOR for Sales_Table

declare SalesRankCursor CURSOR
SCROLL dynamic FOR
select org_id, sales, sales_rank
from Sales_Table
for update of sales_rank


-- CREATE LOOP TO UPDATE SALES RANK in Sales_Table with valid values

OPEN SalesRankCursor

while exists (Select * from Sales_Table where sales_rank = 0)
Begin


FETCH NEXT FROM SalesRankCursor

set @StoreNext = @StoreCurrent
set @SalesRank = (@SalesRank + 1)

update Sales_Table
set@StoreCurrent = org_id
where current of SalesRankCursor

if @StoreCurrent <> @StoreNext
begin
set @SalesRank = 1
end

update Sales_Table
setsales_rank = @SalesRank
where current of SalesRankCursor

End


CLOSE SalesRankCursor

DEALLOCATE SalesRankCursor


Any ideas?