most of the times, login errors are simple matters such as mistyping email or password.
first let me ask you : is email@example.com a valid email address?
If so, then have you tried to simply reset the password by going to http://www.(your-install-domain).com/go - you should receive a new password in your mailbox and then try to log in with this new password.
If you tried all this and still get the same "error", please provide us your error.log (or whatever php error log) file contents.
Regarding not finding logs on this failed login attempts, and if you are running the Apache web server, add this to the .htaccess file in toaster root
php_flag log_errors On
php_flag ignore_repeated_errors On
php_value error_log /path/to/your/erro/log/file
Also you can provide us phpinfo configuration to speed things along.
Let us know if this works for you now, we will make sure this get fixed timely so you can get to work with your install asap :)
Thank you for using SeoToaster!