I had a problem with my ITB last January. It was at the outside of my knees. I used a stretch from Running Well and that cleared it up a treat. Use that now pre-runs and I've *touches wood* not had a problem since.
I'd agree with AG about the long run. Took my PB from 20:52 to 20:20 in the space of five weeks during recent marathon training and I predominantly attribute it to the much longer runs that I had been doing in preparation. I'd also suggest adding some interval and tempo running to your schedule - perhaps replace one of your HIIT sessions on the bike with alternating weeks of a tempo session and an interval session.
I was buzzing as we started into Sefton Park, hitting 20-miles in around 2h50, and had to leave my running partner so I could press on as he was slowing somewhat. Ended up doing the last 6.2-miles in about 49-minutes to finish in 03:38:18, which I was absolutely overjoyed with.
Really loved some sections of the course - the tunnel was an interesting new environment for me and the drums at the exit were epic, crowd support at the finish was phenomenal and the little square, just before the tunnel entrance, was wonderful after the tedium of the industrial estate/docks.