When using TP 5.6 with QA Director, I could never stop testing before it finished. I tried to abort the execution from QA Director, stop TE and TM servers, stop applications and processes from Task Manager, ... none of those works.

After installing TP6, I am glad to be able to abort testing from QA Director in most of time, but occasionally, I still can't abort execution.

What factor causes this problem? How can I stop executing test effectively?