my Wordpress (content management system) plugin caches my sidebar elements as files in /sitefolder/wp-content/widget-cache/

what i did is set 777 for all folders from wp-content and up, but still my php script appears not to be allowed to delete that files in "widget-cache" folder. these files also have 777

I want to ask whuch Appache setting should i check? Which probably security settings can prevent this deletion of files?