Thank you
I have do some test to diagnose my problems.
Avast seem not to be the cause. Problem occurs even in safe mode (mean Avast add-on disable). Problems also occurs on FF (safe mode of course), and seem not to happens with Chrome (need more test though).
Problems probably lies in my ISP's automatic DNS because it does not occurs before (when I use google DNS).
BTW, I still think there are some preferences in PM that related to it because the page does not loading at all, but immediately show me the error. I have never see this behavior before. Should any update in 24.6.1 or FF 30 related to this problem?
I will use DNS benchmarking tool you recommend latter when network load are lesser, for better accuracy.