I activated the error logging per the instructions and tried to edit an existing record (which failed). When I checked the error log file, it was blank. I made sure that the file and directory permissions were set to write and that the value of error.logs in the config.ini file was set to true. Tried again and the error log was still blank.
When that didn't work, I modified the .htaccess file in the root of the installation as per the instructions (setting the value of php_value display_errors from 0 to 1). The only error messages displayed on the screen were the ones that I previously reported.
I am using Dreamhost for the site if that makes any difference.