Just to make sure I understood that correctly: Did you open a 2.2 project in 2.3, then opened the same project in 2.2 again? If so, project files are not necessarily forward-compatible, and this is especially true for 2.3 as it has massive underlying file structure changes, so that has no chance of working. If you want to use 2.2 again, you'd have to load the (2.2 format) backup you made before opening the project in 2.3.