It seems that you have not enough memory on your hosting.
Please, provide us with your error.log (or whatever php error log) file contents.
And it will be greate if you could provide us with output of phpinfo() function.
To do it please create php file that contanis just <?php phpinfo(); ?> in your web root directory, and open it in browser http://YOUR_DOMAIN/NAME_OF_FILE.php
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/error/log/file
With this information we will be able to provide you with the technical support.
We are looking forward to your reply.