Stan you need to give that bag some special attention. Cat pee smells the way it does because there are some pretty persistent alkaloids in it which not even bleach will shift.
http://www.faqs.org/qa/qa-7780.html
http://www.thecatsite.com/Care/48/Combat-Cat-Urine.html
Failing that, I reckon you should take it to a dry cleaners.