In addition to replies so far, my experience has been once it went the first time, there's a tendency for it to go again, especially on long runs unless you keep your regime up. The temptation will be that once you've got rid of it to give it all up, however this is usually the point it comes back - particularly during a really long run.
For me, I do various ITB stretches (along with other muscles - they're all connected after all!) at the end of each run, and look to do some ITB rollering at least 3 times a week - more if my training mileage is high.
I'm also looking at taking my ITB-roller - an empty beer bottle - with me on my planned Ultras to do at set checkpoints; e.g. a quick 10 rolls every 20mi or so.
Generally 3 x 10 rolls (slowly up and down the outside of the thigh = 1 roll) during my rest between other core exercises does the trick. It's bloody painful, but worth it in the long-run.
Best of luck matey:)
SS
P.S. Whilst you are looking to get over it - stop running altogether. A few weeks of intensive ITB treatment as described in the posts above until it goes completely (& you should be able to tell from whether you're walking pain free). Then slowly build the mileage back up.
When last getting over it, I would walk for 10 minutes to warm up run 5/walk 5/run 5/walk 5/run 5 before walking 10 mins back again. I would do this a couple of times a week, and each week increase the run/reduce the walk until you're running continuously for the whole period. After that, you can start increasing to what you were doing before, but remember to keep up the stretches and rollering to ensure it doesn't come back again.
