DisplayLink Screen Saver Issues
I also noticed screensaver problems after installing a USB-DisplayLink adapter on my Mid 2012 MacBookPro.  Except my problem is that periodically screensaver kicks in even though I've been typing and mousing.  There are screensaver error messages in /var/log/system.log but I'm not sure they are related to this issue.

All screens except the DisplayLink screen blank out.  FWIW, I use a USB keyboard almost exclusively, and wonder if that is part of the problem.