Hi,
Few notes to the query. In the inner select use alias for the table name. I take it, you're using the same table (or view) in both queries so try modifying the query to something like:
where INV.Date_Imported BETWEEN '10/1/2010' AND '12/31/2010'
AND INV.RecID NOT IN ( SELECT inner1.RecID
FROM [VW_Invoice_All] inner1
WHERE inner1.Date_Imported > '1/1/2011' )
Also instead of using literals in the statement try changing them to bind variables.
About the conditions, if the table is the same in the outer query and the inner in-list select, I don't quite understand why you have basically the same condition twice. Could you post the whole query?