[Rainer Listing]

This is a relatively common problem. Still happening to lots of users VP12 with build 726 and also Movie studio. May be more common with dual monitor systems, apparently not related to video card, render threads, faulty RAM, DRAM preview, Quicktime version, GPU acceleration. The workaround is to open the dialog from a project with just a short (e.g. generated) clip, cancel the render, then open the project you are working on from the file menu. Anyone can pin it down would be great.