Any runners here? Need advice.

[catinthedark]

Sorry for the long backgrounder, but here goes:

I've been running for years, but have just recently come back from a stress fracture in my hip (due to running). I started running again (very short distances at first, lots of days of rest in between) in June, and am back up to 6km (4 miles) about four times a week. I feel great when I'm running, breathe steadily and easily, and have been slowly adding to my mileage. I'm not by any means dead tired when I get back, nor are my legs tired - but about an hour later - look out! I have muscle fatigue/pain in my legs for the rest of the day (oh, and possibly a touch of bursitis now in the other hip - dammit!). I warm up and stretch afterwards. I just bought new shoes, so that's not the problem. Anyone have tips?

Thanks!