Since yesterday night I get a "500 Internal Server Error" when trying to access my wordpress page (backend still working). After deaktivating Newsletter-Plugin the problem was solved.
Then I updated the plugin, but I can not activate it: I directly get a screen with the "Internal Server Error". The plugin is then NOT activated, but backend and page works fine.
Debug mode of wordpress did not show any Newsletter-errors. I also use qtranslate on that blog.
PHP Version : 5.5.11 / 32Bit OS
Memory limit : 268435456 MB
Memory usage : 7.13 MB