Can you press `Shift+F12` when that happens, and see if there's any messages that seem relevant in the Console tab?
"Uncaught TypeError: Cannot read property 'pWindows' of undefined"
I should also note that somehow it did mostly work last night, except that my library wouldn't display any games. I suspected that was because I just bought the bundle that added 151 of them and it was overwhelmed.
I think this may have something to do with https://github.com/itchio/itch.io/issues/566 — it looks like some of the 151 download keys generated for games in the bundle may be partly invalid, I know Leaf's looking into it, so the issue might resolve itself soon. In the meantime, I'll add a protection to the app to make sure it ignores invalid download keys.