PHPStorm closes all opened files and then freezes

Hello,

I've discovered a strange behaviour of PHPStorm when working on a project.

All of sudden PHPStorm closes all opened files without a warning. No menu item is selectable, the whole application is frozen.
The only possibility to close PHPStorm is using the Windows taskmanager.

Is there some kind of log which could give me some information about what's going on?

Best regards