That is a MySQL limit. You need to edit the MySQL configuration to increase the limit. If you don't manage your own server then you need to ask your host or server person to do this.
However, that is a strange error to be getting on the index page. This might be due to an addon. Try disabling your addons by adding this line to your
library/config.php file:
Code:
$config['enableListeners'] = 0;