So after installing iMovie today, it crashed right away and even after deleting the preferences file, same issue. I did a quick search and it appears that other people are having the same issue. EDIT: I upgraded to 10.3.3 using the FULL installer and still no dice. Can anyone tell me if the problem persists on the 10.3.4 beta? I am using my MacBook Pro with the lid permanently closed and a Samsung 1080p monitor (yes, lame, I know) that's connected via a Satechi USB-C hub's HDMI port. Is there some kind of workaround? How is this possible that 6 months after High Sierra's release and a full THREE point releases, Apple's OWN iMovie software won't work properly?