There was a good article on ITB's in this months RW (Jan 2009) which gave between 4-24 weeks for recovery depending on the severity. I guess if it's the first time you have had this problem (like me) then you won't know the severity.
I managed to get a race on Sunday and it's the first run for about 3 months without any pain at all. That's not to say I have taken 3 months away from training. I managed to maintain plenty of CV activity and used the time to experiment with various stretching routines. As a result my warm ups are approaching half my time in the gym.
The key for me was stopping running completely (the last 4 weeks) and thats when the improvement started to happen. Prior to that I was doing the odd 20 minute session to see how it felt only to discover that it still hurt.
I guess the bottom line is that everyone is different in how they heal and also their tolerance to pain so the recovery time is never going to be an exact science.
Hope this helps