Is it possible to describe exactly what you had done in the editor before you saved and were unable to reopen the project. If you could also link us your log files in your saved folders that would help. You can locate those in the (project Name)/Saved/logs.
Just wanted to check and see if the crash that has been occurring is still happening when you attempt to open the map. If so, could you please provide your log files so that we can better investigate the issue. They can be found by using the path:
Just wanted to check in and see if the issue is still occurring since the 4.2 update has been released. There have been many bug fixes released with the 4.2 update and hope that the crashing issue has been resolved, If the crash is still happening, please be sure to let us know so that we can further investigate.