This is happening to me on 9.5.21, the exact same issue that people are having here.
NEW (BETTER) SOLUTION. Better because I was able to open my original troublesome project.
I opened an empty project. Then I loaded my project and did not activate. It loaded with everything disabled (normal behavior).
Then, I closed the initial empty project and automatically Cubase activates my other project (normal behavior).
Cubase loaded up the tracks/instruments, but then it started hanging again. BUT, then I waited, and waited…and waited. And it finally opened up as fully functional - hooray, my original project was back!
I quickly saved it under a new name and have not had the same issue since but I’m not confident it won’t happen again.
Was it a bad plug? Maybe. Can so many things go wrong when there are millions of messages going back and forth inside a machine we’ve programmed ourselves to trust? Yes. Is it sometimes unexplainable and strange? Yes.
As humans, we love identifying a ‘one cause’. I’m still curious as to what is that one cause that results in this mess.
Hi zooterman,
Will give it a go this weekend & let you know the outcome.
Here’s Hoping. 
Still NO Word from Steinberg.
Glad i’m not the only one with this problem !!!
Mike001
Here’s why we know it’s a Steinberg issue, in my case:
- These sessions opened perfectly before 9.5 (this has been happening to me since then, but much more often after 9.5.21).
- Since then, these sessions crash (disappearing act) when opening and getting to a certain plugin.
- Sometimes the same session will NOT crash at all when opening again a few times.
- Sometimes the session will open fine in Nuendo 8.2 when it crashes Cubase, and sometimes the opposite.
I haven’t added any new plugins in months.
Trashed preferences, yes, which didn’t help.
(On a side note: I understand that software companies make mistakes all of the time, but Steinberg’s abysmal customer service/support, both with service tickers and here in the forums (i.e. no communication about these things) is driving me away from their products. Man, would it make your customer base much more happy and willing to stay on Cubase/Nuendo if you could get your act together with customer service – use Waves as a model.)
Also, when I delete the tracks that make it crash before activating the project, it loads fine and then I can re-import those tracks from an earlier version. After that it doesn’t crash when loading. This says a lot to me about it being something in Cubase.
The same for me. I made a new Project in CB 9.5.30 and save it without problem. I tryed re-opening the day after and it crashes (i.e. cubase closed).
I tryed opening first another project (working) and after that the crashing project. It worked several time but now seems not to work any more.
I would like to revert to a previous CB version (9.5.2?) but I am not sure what I have to do (I have to disinstall CB 9.5.3 and then reinstall everything?)
That a very annoying issue!
I attahced the crash dumps…
Steinberg, please help!
Same issue again, apparently what I had thought was fixed because I saved the project to a new name.
This sucks!!!
The same for me (windows 10 64bit+UR242). I made a new Project in CB 9.5.30 and save it without problem. I tryed re-opening the day after and it crashes (i.e. cubase closed).
I tryed opening first another project (working) and after that the crashing project. It worked several time but now seems not to work any more.
I would like to revert to a previous CB version (9.5.2?) but I am not sure what I have to do (I have to disinstall CB 9.5.3 and then reinstall everything?)
That a very annoying issue!
Steinberg, please help!
Steinberg
Where are you 
Mike001
This looks like the same issue as the below.
Mike001
I am also having this problem, also when opening Nuendo 8 projects in Cubase 9.5.3
Very annoying and serious problem!
Disabled all plugins, no change.
This is a code red issue, I hope it’s gotten noticed
Also having this issue, I cant open a project that worked fine before the update, no saved version will work and I can’t open it in Cubase 9 without losing a load of my effects because 9 doesn’t have as many insert slots… total bummer. Please fix!!! Will see if I can roll back?
I tried using the method of opening another project first then loading the one that wont open but not enabling it, this didn’t work, Cubase crashed instantly. Every crash just makes Cubase disappear, no hanging, also it crashed before it looked like it loaded anything. This is Cubase 9.5.3, 9.3.21 works fine for me.
Thanks a ton for posting this, you saved me loads of hassle, I just grabbed the app from my time machine backup and replaced it and now my project opens again!!! thanks
Just discovered that one of my other projects that I started in Cubase 9.5.21 and then worked on for two hours after installing Cubase 9.5.3 does not load in Cubase 9.5.21!!! Only versions of the project that load are the ones saved prior to the update.
So in order to run it I probably need to re-install Cubase 9.5.3?!!.. if I’m lucky that will work, but then it could just be corrupted…
This is insane… either try that or just lose 2 hours work.
I wondering if I can actually have both Cubase 9.5 versions in my app folder? hmmm
Steinberg please sort this out ASAP!!!
So… I found I had copied the Cubase 9.5.3 to my desktop, so I placed it back into the app folder. Managed to get the project to open but I can’t export it as it crashes instantly each time… so basically I don’t know where to go next with it. seriously not cool.
Seems like I wasted a lot of money on Cubase and should just move on to studio 1 since Steinberg is of no help what so ever. Thanks for nothing.
I must say that the one thing I find in common the few times this has happened to me, was not the version of Cubase, but the use of Melodyne on the projects.
I have not upgraded to 9.5.
Anyone using Melodyne when this happens? Just a thought.
No melodyne here
Bummer.
I have a whole 12 song project to mix that I have to open up another project first in order for Cubase to load the project at hand. Does not look very professional…
Ugh…
6 other projects working just fine. Have no idea what the difference could be. No new plugs since these projects started.