I do apologize dagon for the loss. It's not a bug really (i.e. a crash), but a design flaw that's pretty hard to fix due to very little feedback regarding dirty/clean changes from the new editor control. Back when I used the RichTextEdit control, there was no question about there being unsaved changes, but with this new one, it has to be micromanaged from the outside world.
Frankly, I haven't had the time to work on something that seems to be so simple to fix, but in reality would take me a weekend. So that's why we post issues like this for you to be aware of. Plenty of people use SUO successfully, knowing there are limitations.
Also remember what you paid for SUO. It's free if you've forgotten. I'm not Microsoft and don't have 1000s of programmers at my command to fix issues, so you have to also keep that in mind when using software you find on the internet.
I have also lost work to this "bug", so I do understand that it's frustrating. However, I've lost work in just about any editor I've ever used for one reason or another. Ever have EasyUO just lock up on you and the only thing you can do is CTRL-ALT-DELETE to stop the service? I've lost more work that way than I ever have with SUO.
This issue is the first one I'll be correcting when I can get back to SUO development. Superslayer has found a few actual crash issues that need to be fixed also.