Ok, fine, yours does not dim. I'm saying that mine does. Which is something that I don't want. Which is the issue here.
Sorry only trying to help.. And since it is not in front of me, I can only guess..

I noticed a post on Intel about this issue, at about the same time as this one..

I searched the internet for info on this, and I read several forums post about Acer adaptive brightness issues..

Two other possible issues causing this could be "Fast Startup" and "Hibernation" because when you startup with thoses feature enabled it uses a saved setting type file.. so disabling those is an option..