15 Beta crashing and HDMI

On my laptop (ASUS), the latest beta woks perfectly (albeit slow). On my desktop (DELL), as soon as something is added to the time line that is a movie clip (ie NOT a still) Resolve crashes into the ether after a second or two. Additionally, I can never get any images (still or clip) to appear in the preview / playback windows.

I use an HDMI based monitor only. Is this contributing? Experience says also a CODEC issue somewhere (I had this with Fusion re: Quicktime which adding the lasted QT addressed)