Error when updating other plugins

solved the problem by following these instructions from here http://wordpress.org/support/topic/plugin-upgrade-failing-cannot-remove-old-plugin?replies=25#post-1303436

1. Make sure your wp-config.php file is chmodded to 0644.

2. Also make sure your .htaccess file is protecting the wp-config file using these lines:

<Files wp-config.php>
order allow,deny
deny from all
</Files>

3. Backup your wp-config.php file.

4. Edit your wp-config.php file putting these lines in underneath <?php:

define(‘FS_METHOD’, ‘ftpsockets’);
define(‘FTP_BASE’, ‘/path/to/wordpress/’);
define(‘FTP_CONTENT_DIR’, ‘/path/to/wordpress/wp-content/’);
define(‘FTP_PLUGIN_DIR ‘, ‘/path/to/wordpress/wp-content/plugins/’);
define(‘FTP_USER’, ‘username’);
define(‘FTP_PASS’, ‘password’);
define(‘FTP_HOST’, ‘ftp.example.org’);

————

I had to enter full path like this
define(‘FTP_BASE’, ‘/var/www/vhosts/MYWEBSITE/httpdocs/’);
define(‘FTP_CONTENT_DIR’, ‘/var/www/vhosts/MYWEBSITE/httpdocs/wp-content/’);
define(‘FTP_PLUGIN_DIR ‘, ‘/var/www/vhosts/MYWEBSITE/httpdocs/wp-content/plugins/’);

works again also with visitor-maps active!