I have been running about 5 miles on alternate days and biking on the
off days for about 7 months. About 3 weeks ago, I didn't do my usual super slow/easy 1/2
mile first and just started my run with out warming up. Yeah, I
know.....

Anyway, felt fine through the run. The next morning didn't
think I was going to be able to walk. The pain is on the anterior iliac
crest back to about the center of the crest , not posterior, and is
intense. I layed off for a week and only cycled and had no pain. Then
ran an easy 2 miles on a treadmill at the gym and the pain returned
full force the next morning. I have seen a chiro and sports massage
guy. No one has been able to specifically diagnose. Just stretch more and come back a bunch more times.

Over the years I've had the usual aches and pains running, but this one
seems different. Doesn't really bother me after the first 5 minutes of
the run. The pain returns about an hour after the run and is pretty
intense for the next day as well before subsiding. I can stretch
through it (using the feet crossed IT stretch) and it immediately feels
better, but if I sit for 30 minutes it is back again.

Anyone experienced this or have any suggestions?

I just don't want to further damage something by ignoring it.