I have had this and did lots of research. The most valuable thing I found was 'rest'. It is also the most unwelcome if you are pushing for a deadline. We all hate not to train and run. But what I read made clear that there is no real understanding of ITBS and conflicting advice. Some recommend stretches, but there is medical eveidence that suggests the ITB cannot really be physically 'stretched', so any benefit from stretching is probably limited. The research I did, and followed, said that rest is really the most positive thing you can do. IT has to be total rest. not just reduced running. Give it a total break for a month. Then start slowly, 2km max, maybe 3 times a week. Then build up, slowly. At the first sign of anythign wrong - stop and walk. Never push it. It will go.
In terms of a cause, the main suspect is running suface, camber, hills, and repetitive movement. The last of these is not to be underestimated. You may be fine doing hills, or road running, but not if you do it all the time. Mix your running, and you are more likely to avoid repetitive strains (IBS and lots of others too). And you will be a better runner too! So don't run the same course, same road, same hill every time. Change your training and mix it up.
Good luck.
