Thank you for the info about the Stream Filter, DavidR!

About your questions:

  1. XP SP3 - So for me that option doesn’t make any difference!
  2. Latest version, 2015.10.2.2215

I’ve disabled all the protection for a test, and my CPU still goes to maximum almost instantly when flash player is involved in some way. So, I believe avast! is not the problem here. Thank you anyway!