Cannot redeclare _simpleads_filter_process() (previously declared in /home/automat2/public_html/sites/all/modules/simpleads/incl

I get this error when activating simpleAds filter:

Cannot redeclare _simpleads_filter_process() (previously declared in /home/automat2/public_html/sites/all/modules/simpleads/includes/simpleads.filter.inc:26)