It might be helpful for some of you:
I received Error 500 right on the next step after running setup.php (while upgrading) - first page loaded fine and after logging in Error 500 appeared.
So, in my case it was that (i'm not sure, but that is the fact) setup.php chmoded zenphoto (directory) to 777 and my server returns 500 Error in this case. So, I chmod zenphoto/ back to 755 loaded setup.php again, logged in, receiver Error 500 again, chmod zenphoto/ back to 755 pressed F5 (reloaded page with sending form data again) it worked fine. Pressed GO! button at the bottom and that was it - upgrade finished successfully.
Now, to the developers - please do something about setup.php so it would not chance attributes to the directory or, if that is necessary - mention this somewhere in your instructions.
Cheers!
Comments
http://www.zenphoto.org/support/topic.php?id=2#post-80