500 Internal Server Error - Problem after upgrade

I upgraded to the newest version of ZC and installed the security patches. I have not renamed my admin yet.
I can access the admin panel.
I CANNOT access the web site. I get a "500 Internal Server Error".

I have no idea where or how to solve this problem.
Any help or leads are appreciated.
thanks.

This error is the usual result of an offending file/folder permission setting.
Easiest to ask your host to reset(chmod) your files & folders to default - or you can check - especially those files with recent changed dates