There are no known problems with the latest nginx versions, so the latest supportest version is the latest released version.
Then you might want to take alook into the nginx error log file to see what is causing this. a 500 error indicates a problem with the setup / user permissions or ssl cert and not a general incompatibility.
Or I don´t get anything, this is the page where ISPConfig should be: http://31.192.226.88:8080/ It works fine when I use nginx 0.7.