Funny - I'm not seeing any issue with WindowBlinds 8,0 and Avast 8.0.1489 (the latest version) on my Windows 8 laptop.  It might be a driver issue with alexgerry's system or missing updates.  I've used several different themes (mostly the newest essorant themes...) and aren't experiencing the problems that have been reported.  The only issue I have noted is that when I run the Stardock-made Win8 Metro theme there's a tendency for it to "stick" to the top of the screen if a window gets too close to the top - not having any other major problems with newer skins.

BTW - I reinstalled the Sabertooth skin from WindowBlinds 7.41 and it works fine on the system - not sure why it was removed from the preinstalled skins but I'm submitting my vote to put it back in.

I don't use Avast any more but I have seen this as well on Win7/64 and WB7.xx  with most skins I used. Most notably, when disabling Avast for a specified time period. The dialog box that opens will continue to shink down to nothing. IIRC, Tab or Shift would make the box full sized again. You have to be a quick clicker to hit those buttons though.