I've been dealing with this lately too. Came off a long run and could barely walk the rest of that day. I pushed it, thought I had a sacral stress fracture (didn't), but took two weeks off. It went away, but came back as soon as I tried running again.
I had it checked out, and had a few things going wrong. One side of my pelvis wasn't moving in the full range of motion (it was "locked," as a chiro said) and wouldn't move forward like the other side; my stride was pretty uneven as a result. The hip flexor on that side was also significantly tighter; which came first, I'm not sure, but now I'm working to fix both.
You saw a chiro - did he/she do any work on you? I've been adjusted (specifically the SI joint has been released, but the other stuff is helpful too) a few times and it's worked really well so far (three weeks running without pain so far, haven't built my mileage above 50/week yet though). My walking is a lot more even, and I'm constantly stretching my piriformis and hip flexor. It wasn't an instant change (plus my walking stride is awkward as I re-learn to walk with equal-length legs), but it's an improvement and I imagine it will keep getting better.
In addition to this, I'd been to a PT and the glute on that side was barely firing. Again, not sure which led to which, but now I have to fix all the stuff going wrong.
I know chiros evoke some skepticism - some deserve it - but the guy I went to is very straightforward, was an athlete himself, and works with a lot of runners. So try that out if you haven't (it sounds like you've found one though). Try it in tandem with a PT if that doesn't seem to do the trick itself. Good luck.