[Plugin: Visitor Maps and Who's Online] Fatal error: error traversing GeoLite City database fil

esmi is correct, you can recover control this way.

That error is usually caused if your PHP does not have enough RAM to open the database file that is 30M in size.

Some wordpress installs run out of available memory because it is set
too low in PHP.

Try one of these methods for increasing the amount of memory a
PHP script may consume (most people just do #3)

1. If you have access to your PHP.ini file, change the line in PHP.ini
If your line shows 32M or less, try increasing it:
memory_limit = 64M;

2. If you don’t have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 64M

3. Try adding this line to your wp-config.php file:
Increasing memory allocated to PHP
define(‘WP_MEMORY_LIMIT’, ’64M’);

4. Talk to your host about their recommended solution.

Here is a related article I wrote
Checking WordPress for Low PHP Memory Limit
http://www.fastsecurecontactform.com/php-memory-limit