Crash on load after crash on render

While trying to render an hourlong project yesterday, KDEN got to the end and then crashed, warning that the resulting file was probably corrupted. It wasn’t, actually - I could play the video. Now when I try to start the app I get a “last session crashed” warning, and the offer to rebuild settings. Regardless of what option I choose there, it crashes again and won’t open.

I downloaded the very latest version just now and it takes me to the welcome screen (choose your preferred video format, etc) and just crashes when I click on Start editing. Running iMac Sequoia, Intel Core i5.

Are there library files or caches I should be deleting manually, or something? I would expect a fresh install to work, and it does load as far as that welcome screen.

Thanks in advance - dead in the water.