Now it says "Failed to load common event data." ?The easy way to fix this is replacing your project's *.rvproj2 (icon has two cog wheels in it) with one from a new project.
I haven't got any backups.Well, then replace the Data\CommonEvents.rvdata2 with the one from your latest backup.
I don't know which files are corrupted and I haven't got any backups.Sounds like something in your project has become corrupted.
All you can do is replace those files from a new project until you stop getting the error message. Then you have to figure out what you've lost and key it all in again.
Backups are excellent.