Hello.
I spend the whole morning transcribing a project from Cubase to Dorico, with various XML Import that made no problem.
I closed the project to get a coffee.
Once I reopened the project it says “Error Opening File”. I searched the web for answers but find none. Even all of my backups give the same error…
I actually needed this project for today… 
I add the link to download the file, since in other posts it was required
I hope I can get some help.
Here’s a fixed version of your project:
If you really are still using Dorico 1.1.0 rather than Dorico 1.1.10, I recommend you update as soon as possible, as the problem that we know of that can cause this kind of corruption was fixed in Dorico 1.1.10.
Awesome Daniel, thanks!
The strange thing is that I’m actually on Dorico 1.1.10 (Aug. 2017 Says it) …
Well thanks anyway 
OK. Had you done any kind of split flow, change instrument, etc. operations while working on the project? It’s possible that you have uncovered a lurking bug, but unless you know what you did it may be difficult for us to find it!
Yes.
I had started this with a “Synthesiser” but then realized that I only needed a bass line so i switched that to “Synth Bass” with the “change instrument” thing in the setup menu (the one you click on the small instrument name in Setup window)
I think that could be the moment when it broke up.
The rest is imported from Xml, but its a copy and paste thing. e.g. on cubase I select all strings, export to Music Xml, Open the Strings.xml , copy the music there and paste onto the other project. Same for winds, brass and piano/harp/keyboard.
Hello
I have spent 2 weeks working on a project which currently has 6 flows (movements for violin and piano).
Today I get the ‘error opening file’ error message, even on the back up files. It was all working fine last night!
PLEASE advise, I don’t want to lose all my work. Give me an email address to send the file to if you can help
BS
Score user for 30 years, wishing Dorico had been around all that time!
Can you email me project to me, Brian, and we’ll take a look as quickly as we can? My email is d dot spreadbury at steinberg dot de.
Thanks Daniel I have emailed it right now (but under my real name).