Cannot Upload Plugins
I am getting a fatal error notice each time I try an activate a new plugin. I am trying to upload Newsletter plugin, which uploads fine if I switch the theme to Thesis or other themes, but returned the message below when I switch back to Classipress, completely disabling the site. I have reloaded the Theme so am in a bit of a fix. This is the same for every plugin I try. Help!
Fatal error: Cannot redeclare widget_newsletter() (previously declared in D:\Hosting\4231672\html\
wp-content\plugins\newsletter\widget.php:4) in D:\Hosting\4231672\html\
wp-content\plugins\newsletter\widget.php on line 4