ok, i added the field list, so now my query looks like this:
INSERT INTO table_stats (Area, TimePeriod, Year, Type, Number)
VALUES ('AREA1','January', 2007,'typeA',
(SELECT Count(ID) FROM table1 WHERE [Area]='AREA1' AND [SalesDate]>=#1/01/2007# AND [SalesDate]<=#1/31/2007# AND [Type]='in'))...