Got in touch with Raghuveer Singh, and he and the Adobe bug team are on it. I gave him a test file, along with display and system details so they can get further to the bottom of the issue.

I don't know how they let a bug like this pass through. The stranger thing is my co-workers aren't experiencing the bug. Only my machine is dealing with it, and we're a team of 8 designers. One of my co-workers claimed they experienced the bug, but after updating to Mojave, it went away. Not for me! Anyway, hoping they fix this sometime this week. Might be longer, though.

Same issue daily on my iMac 27 OS 10.13.6, "Can't finish previewing." I restart and hope my files are still there. They have been there, back to the last Save. I'm not going back to 2018 though.

Same issue. Went back a version to 2018 for all Adobe programs as a temporary fix.

I'm having the same issue.

I'm having the same issue.

Same problem, it is getting more frequent now. Almost unusable.

Same problem, not enough RAM to open ai files, have to restart program constantly.

Exactly the same issue, this is so frustrating. I have High Sierra, working on a mid 2012 MacBook Pro. No issues before the update.

I solved it with reinstalling previous version.
http://prntscr.com/l8zcah

Very disappointed, adobe.

how do you reinstall the previous version of illustrator?

I wonder: Is Adobe testing their software before launching it?

Yep, same, v23 also. Never had this issue before in 20 years! But even on basic files it's happening daily.

Same problem here, working with old version until problem is solved.

same problem? is there any update on this issue

Same issue here. I was reading all the messages last week, and I solved my problem with going back on previous version. I will work on that one until they fix this issue.

Exact same issue here. Error happens about every 10 minutes after opening a file. Illustrator is unusable in this condition.

Same issue here. Extremely annoying, I need to restart Illustrator about three times per hour. Not workable. Going back to CC2018.

So disappointing for a such big application that has been released without any bug testing, which affected thousands of users around the world!

After working for a while in Illustrator (perhaps a little under an hour) doing not very taxing graphics, the preview turns off and defaults to outline. Attempts to turn the preview back on fail with an alert complaining that the app has run out of memory. Activity Monitor confirms that Illustrator is using considerable memory, typically well into 2 Gb. Workaround is to save the document, quit and restart.