Error 500 after hitting the Cleanup button at the end of the installation

[astropos]

Solution: Just in case anyone gets this problem, in my case the problem was that I followed a tutorial that insisted on disabling cgi.fix_pathinfo, in the php.ini file.
When setting cgi.fix_pathinfo =1, the problem fixed!

Further info: I've done loads of these. All Ubuntu server based. It's permissions.
If you chmod 777 the /install directory (and all files) before the install, it should work ok.
US attempts to delete the files in this dir as part of the cleanup, but hits a permission denied.

And yes, repeated installs will mangle your init, clear down and start afresh.