Please email supportdos@larian.com. On PC the report.zip file generated by the D:OS support tool will include crash dumps, system information, etc, as well as any saves that were written to the save folder (partly or not). On Mac, I have been told crash reports are collected inside the Console application. When emailing the crash reports, the end section (list of libs) can be omitted. User System Profiler to collect system info. To diagnose hangs you can launch Activity Monitor, then select Divinity and press the Sample button.
Try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder. After that try starting a new game and see if you can save. This folder contains the profiles, saved games, configuration files and a level cache folder. Deleting or renaming it will get the game to recreate it on startup; playing the game from a different Windows user account would effectively do the same thing (don't know about Mac).
