The Column Prefix 'h' Does Not Match... Parses Ok

I get the error below from the following SQL. This SQL worked until I tried adding a third table "ship_to_salesrep". If I comment-out the third join and the last condition it works.

I have tried putting the "r" table in the FROM statement and still it does not work. Everything looks right to me -- what am I doing wrong?

Server: Msg 107, Level 16, State 2, Line 2
The column prefix 'h' does not match with a table name or alias name used in the query.


SELECT distinct
m.inv_mast_uid,
CONVERT(DECIMAL(10,4),0.00) as 'inv_cost',
CONVERT(DECIMAL(10,4),0.00) as 'oe_cost',
l.invoice_line_type, s.cost,
h.invoice_no, h.order_no, h.order_date, h.invoice_date, h.customer_id,
h.ship_to_id, h.ship2_name, h.ship2_address2, h.ship2_city, h.ship2_state, h.ship2_postal_code,
h.terms_desc, h.po_no, h.salesrep_id, h.salesrep_name, h.period, h.year_for_period,
h.ship_date, h.total_amount, h.amount_paid, h.terms_taken, h.allowed, h.paid_in_full_flag,
h.last_maintained_by, h.printed, h.printed_date, h.shipping_cost, h.invoice_reference_no,
h.invoice_adjustment_type, h.memo_amount, h.bad_debt_amount, h.invoice_class, h.period_fully_paid,
h.year_fully_paid, h.approved, h.other_charge_amount, h.tax_amount, h.original_document_type,
h.date_paid, h.print_flag, h.print_date, h.customer_id_number, h.date_created, h.date_last_modified,
h.consolidated, h.sold_to_ah_uid, h.sold_to_customer_id, h.invoice_batch_uid, h.sales_location_id,
h.source_type_cd,
l.qty_requested, l.qty_shipped, l.unit_of_measure, l.item_id, l.item_desc, l.unit_price,
l.extended_price, l.gl_revenue_account_no, l.gl_salse_tax_account_no, l.pricing_quantity, l.line_no,
l.sales_cost, l.commission_cost, l.other_cost, l.other_charge_item, l.exceptional_sales, l.pricing_unit,
l.invoice_line_uid, l.invoice_line_uid_parent
into jch1.dbo.sales_history_invoices
FROM
invoice_hdr h, invoice_line l
left join inv_mast m on l.item_id = m.item_id
left join inventory_supplier s on m.inv_mast_uid = s.inv_mast_uid
left join ship_to_salesrep r on h.ship_to_id = r.ship_to_id
WHERE
l.invoice_no = h.invoice_no and
h.invoice_date >= '2006-07-01' and
h.invoice_date < '2006-08-01' and
l.invoice_line_type = 0 and
m.inv_mast_uid is not NULL and
r.primary_salesrep_flag = 'Y';


Thanks,
Charles