Struggling to shake off a similar problem myself.
I aggravated my ITB last October and that has seemingly now morphed into pain in the left hip and glute. I have little pain cycling and running up hill but anything more than a jog on the flat and the pain kicks in. Consequentially, a 10km run around my local hills leaves me in pain and hardly able to walk the next day whereas 14km around the Long Mynd with 1000m climb and nowhere flat was absolutely fine.
Daily regime of stretches, core work and foam roller seem to be helping a little but will be following this thread to see if anyone has any bright ideas!