ActiveX behaviour change causes seizures.
The new ActiveX change will, apparently, cause seizures, and prevent ActiveX controls from running at all until clicked on. At least, that's if you believe TechWeb
Sadly, SANS chose this page, with its stunningly inaccurate and poorly worded description of the new ActiveX change, as their main link to describing what's going to happen.
The real deal of the change is far simpler. If you want to send mouse input (including "mouseover" messages), or keyboard input, to an ActiveX control, you have to select the ActiveX control first to 'activate' it. That's all - the controls will run; music will play, the pigs will still dance, but you just won't be able to tickle them until after you click (or tab and space/enter) on them.
So, no, ActiveX will not cause seizures.