We are not using any optimization software to my knowledge, we do run a general system maintenance package, advanced system care ultimate, but that hasn't interfered with any other game/program and the internet connection. Will try running the game while disabling ASC Ultimate and see what results. I do have a few other programs running all the time, will try turning them off one-by-one and see if anything changes.
What we find most strange is the way the internet connection gets blocked the game is running, but is not blocked if the game is running but in the background (using Alt-Tab). Really cannot figure that bit out.