Ever since I upgraded to Adobe Illustrator 2021 v25, I've been getting several strange messages, primarily when I'm trying to save files. The messages as best I can remember are as follows:
This file has been modified outside of Illustrator. Are you sure you want to continue?
An unknown error has occurred.
In most cases, the second error message occurs when I hit continue to the first. The strange thing is that, to the best of my knowledge, the file hadn't been modified outside of Illustrator. In every case, whenever I get these messages I am unable to successfully save the file and I usually have to shut down the app.
Has anyone else experienced this problem and if so, what is the solution?
Thanks to everyone who responded. I ended up resetting my preferences and that seems to have foxed the problem. Here's the procedure: Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (macOS) as you start Illustrator. The new preferences files are created the next time you start Illustrator.
This does happen ever so often to me as well, especially when working with network shares. Worst thing that happens next, if you manage to continue, is that the file is corrupted and only a temp-file remains and a hidden AI-file, which in most cases is useless.