I have a program called ProntoProEdit NG that I have been using for many years.
It Reads and Writes .pcf files, these a essentially ZIP files renamed. However since installing Avast I noticed that it was about 10 times slower accessing these files.
I eventually found disabling the behaviour shield fixed the problem, however when slowing the program down the shield showed no activity.
No matter where I try putting the program or its files in the exclusions I cannot get the performance to improve except for stopping the Behaviour shield.
Also, how are you disabling the Behavior Shield? Just by turning it off in the GUI? No reboot or anything necessary - simply turning it off resolves the problem immediately?