I'm currently training for a marathon and have over the last week developed symptoms that seem to indicate ITBS 
It started on Tuesday I only did just over 3 miles but I could feel a slight niggling and clicking sensation in the outside of the knee, same happened on Wednesday.
On Friday i went out set for a 9 mile run, I was going a bit faster than earlier in the week and didn't feel any problems until at 7 miles I had to stop and redo my lace. When I tried to run again after the stop I had really sharp pain in my knee when i tried to bend it and I couldn't run!
I had no pain on walking though so I strided home and kept trying to run, after about 100m the pain had subsided and I ran home pain free 
On saturday I ran 19 miles, again there was no pain whilst running but when I had to stop to cross roads etc... I had the same stabbing pain in the outside of my knee when i tried to start off again, which again gradually subsided!
Does this sound like ITBS or something else? I have had new shoes 5 weeks ago (wondering if they could be the problem) and I wear orthotics, I have had video gait analysis that shows a neutral gait. It is very hilly where I live but this hasn't caused problems before!
It is aching when I bend it walking today so obviously getting worse 