I also tried renaming the newsfeed folder and then activating again..still lead me to a 500 internal server error. I then re-named the groups folder deactivated and re-activated still lead to a 500 internal server error. All plugins look as though they have been updated. So i put everything back but still cant use newsfeed plugin :( The only thing i havn't done is completely uninstalled Groups plugin as it says it will delete all content, however it doesnt seem that its the group plugin with the problem, seems like newsfeed.