I think you are on the right track ME! I don't buy into that theory Incharge brings up...I think there are many variables to consider. I know of many who have root canals without a problem and I have a friend in the business that has seen a number of patients with root canals who never develop infections!
However, I do believe a LARGE % of people have problems and most relate to a poor functioning immune system, which in this day is MOST of us!