I'm trying to do what seems to be a simple update, but I'm not sure if it's a good query or not.

Code:
UPDATE Dataflex.dbo.IP042F68 SET PRODUCT='UCORES', GROUP_Col='TSF' WHERE ITEM_NO ='TSF-7070-102-57-25-0000' AND LOC='NY' AND PRODUCT='MISC'
does this not work because the "PRODUCT" field is used in both the WHERE part of the query as well as being a field that's updated? The database is indexed by all the fields in the WHERE clause. Not using all the fields makes the query take about 20 mins (using only the "ITEM_NO" field). Using the query as above takes about one second and says that it updated one row, but really doesn't update anything. Should I be able to do this?

I'm using Connx ODBC driver on a DataFlex database.