Idea as to why this query won't work as expected?

["Aaron Wolski" <aaronjw@martekbiz.com>]

Hi All,
 
I have a query like:
 
select * FROM OrderTable WHERE submitted=1 AND
dateinserted>='1036386000' AND dateinserted<='1036502796' AND
order_status='Shipped' OR order_status='Not Shipped'
 
 
Now.. if I omit the  "AND order_status='Shipped' OR order_status='Not
Shipped'" part the query works fine and only returns 2 results (as
expected). However, with the inclusion of the previous I get all the
results (currently 8) returned.
 
It seems to be ignoring everything before "AND order_status='Shipped' OR
order_status='Not Shipped'".
 
Any clues?
 
Much thanks!
 
Aaron