I took my time posting this because I almost put money in it. This is just a warning shot, if you still like to use avast its ok, not my problem. I did all the other things posted here, like unistall kasperky correctly (with their own unistall) and made a clean install of avast.
I am not a computer expert, but I know a few things.
This problem just looks like its just a compatibility problem rather than a "serius" problem, but for me thats enought to just dont buy the product.
Soooo good luck everyone.
I'm out