Hi June,
You need to turn on all error reporting to see errors. Add these two lines to your mysite/_config.php file:
Director::set_environment_type("dev");
error_reporting(E_ALL);
And add this line to the .htaccess file in the root of your install:
php_value display_errors On
Good news is the front end works fine, so if you are logged in you can post new and edit existing blogs.
And works fine on my production server.
I'm using a mac, so I just renamed new install to mamp_new and renamed old install back in place. I saved a copy of old install when I upgraded.
Hope that helps.
Regards
Scott