I Don't Understand How This Works, However It Works (sometimes)

I use the code below for updating data from a AS400 Liked server. I dont understend how the WHERE NOT EXISTS( sections work however usualy they do, in this case it does not andt I can't seem to find out why.

Does anyone see the error?

Thanks

--=========================================
--Create a local temporary table that hold
--all the data from the source table
--=========================================

SELECT * INTO #TEMP FROM dbo.LINK_LTTSTOC

--=========================================
--Remove table entries that are no longer
--needed or that have to be updated
--=========================================

DELETE FROM LTTSTOCK

WHERE NOT EXISTS( SELECT * FROM #TEMP

WHERE LTTSTOCK.WarehouseNo = LTWHLO

AND LTTSTOCK.Location = LTWHSL

AND LTTSTOCK.ItemNo = LTITNO

AND LTTSTOCK.NumberAvail = LTAVAL

)

--=========================================

--Insert data that is missing or that

--needed to be updated and was previously

--deleted

--=========================================

INSERT INTO dbo.LTTSTOCK(WarehouseNo,Location,ItemNo,NumberAvail,rowguid)

SELECT DISTINCT LTWHLO,LTWHSL,LTITNO,LTAVAL, NEWID()

FROM #TEMP

WHERE NOT EXISTS( SELECT * FROM LTTSTOCK

WHERE WarehouseNo = LTWHLO

AND Location = LTWHSL

AND ItemNo = LTITNO

AND NumberAvail = LTAVAL

)

--========================================

--Remove local temporary table.

--========================================

DROP TABLE #TEMP