The maximum memory allowed for PHP scripts appears to be 10 MB. This is usually set by your server administrator.
You can increase the limit if your web host allows it (Warning: This may be in violation of your web host's TOS. Please refer to it for PHP script memory limit).
The best amount of WordPress is 64 MB.
If you have access to your php.ini file, open it and search for the line: memory_limit. If it doesn't exist, create it and if it exists, modify the line to:
memory_limit = 64M.
If you don't have php.ini access, you can add the following line to your wp-config.php file right after the beginning <?php:
As I mentioned, some hosts may suspend your account for doing this as you are using more resources than you are allowed to, so I recommend you contact your host about this.
From the fatal error you mentioned, it looks like your limit is 10 MB currently.