1. .se project file can be open in TextEdit or other text apps. When anything weird happens, open the .se project file in any textedit app, then copy all timecode and subtitles and paste them to a new .se project. You won’t lose any of your work.
2. If SRT Edit Pro cannot open your SRT file, there might be some problems going with the SRT file itself. Please refer to the SRT part of this post: PremiereSRT Question and Answer.