I had the same problem and it appears to be the DraftSight QL generator. I wasn't sure how to find/delete it, but was able to do so: navigate to the DraftSight application (in the applications folder), hold down "control" key and click on the DraftSight application, select "show package contents", look in Contents?Library>QuickLook, and drag the FxQuickLookDrawing.qlgenerator file to the trash, log out or restart, then you'll be off and running.