Problem With Parallel Query Execution

I have a SQL 7 db with a union query (view), and I'm getting the error, "The
query processor could not start the necessary thread resources for parallel
query execution." This union query has been in place for about two years now
with no problems until just now, though I haven't changed anything. Also, I
have a local copy of the database on my machine, and the query runs fine.

As noted, I haven't changed anything in the query, nor in the SQL settings.
There is a network administrator, so it's possible that he may have changed
a setting, but I don't know what. The query is reproduced below. Any ideas
as to what's going on would be appreciated.

Neil

Main query:
SELECT Tmp.INVCUST, Tmp.SDNBR, Tmp.SDBOOK, Tmp.SDIVCLN,
Tmp.SDPAID, Tmp.SDPRICE, Tmp.SDCOPIES, Tmp.Location,
INVTRY.AUTHILL1, Tmp.INVDATE, INVTRY.SaleSrc,
INVTRY.HoldInit
FROM (SELECT INVDATE, INVCUST, SDNBR, SDBOOK, SDIVCLN,
SDPAID, SDPRICE, SDCOPIES, 'P' AS Location
FROM vwInvoiceDet
UNION ALL
SELECT INVDATE, INVCUST, SDNBR, SDBOOK, SDIVCLN,
SDPAID, SDPRICE, SDCOPIES, 'N' AS Location
FROM vwInvoiceDetN
UNION ALL
SELECT INVDATE, INVCUST, SDNBR, SDBOOK, SDIVCLN,
SDPAID, SDPRICE, SDCOPIES, 'M' AS Location
FROM vwInvoiceDetM) Tmp INNER JOIN
dbo.INVTRY ON Tmp.SDBOOK = dbo.INVTRY.[Index]

vwInvoiceDet:
SELECT tabInvoice.INVDATE, tabInvoice.INVCUST,
SALEDET.SDNBR, SALEDET.SDBOOK, SALEDET.SDINVNUM,
SALEDET.SDPRICE, SALEDET.SDPAID, SALEDET.SDCOPIES,
SALEDET.SDIVCLN, tabInvoice.INVNBR, SALEDET.SDID
FROM dbo.tabInvoice INNER JOIN
dbo.SALEDET ON
dbo.tabInvoice.INVNBR = dbo.SALEDET.SDNBR

(vwInvoiceDetN and vwInvoiceDetM are similar to vwInvoiceDet.)