Now that you've mentioned Image Editor, I kind of remembered, that the first time when C2 closed was when I was doing something with one of the sprites in Image Editor. I think I was closing it, when C2 just closed itself completely. And one time it just corrupted one of the frames. I can't remember what the error was saying, but I had to delete the frame and replace it with other file. Not sure if it's connected to the main topic, but maybe this info will help.
I'm also now starting to think it has something to do with the image editor.
I've always been able to edit for long periods of time on the events sheet without crash, but now that i've been working a lot on the layout and using the image editor, C2 seems to be more prone to crash. I have autosave disabled and save manually every 5 minutes or so. I also don't get any notice.