I've always learned to do cardio on an empty stomach early in the day, and leave at least 4 - 5 hours till I lift later that day. Your body burns the most fat on an empty stomach.
You also don't want to do a large cardio session right after lifting when your muscles are craving much nutrients that they will not recieve. Worse come to worse, do cardio before lifting and sip on protein during it. Then go into your lifting session and make sure to consume protein thereafter.