Set time limit problem when trying to update the options

Hey there,
I have the following message when I try to update my access the settings of the plugin:

Warning: set_time_limit() [function.set-time-limit]: Cannot set time limit in safe mode in /var/www/vhosts/yagg.com/httpdocs/wp-content/plugins/wpmu-dev-seo/wds-files/wds-sitemaps/wds-sitemaps.php on line 40

Does someone know how I can solve this?

Thanks!
Xavier.