Plug in Install fail and Update failure

I have tried to install AKISMET as our blog is being battered with SPAM now and the intall failed, also I’m being asked to update to WordPress V 4.0.01 and I’m getting this message:
The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.: wp-admin/js/editor-expand.js, wp-admin/js/editor-expand.min.js, wp-includes/js/media-grid.js, wp-includes/js/tinymce/plugins/wpeditimage/plugin.min.js, wp-includes/js/tinymce/plugins/wpeditimage/plugin.js, wp-includes/js/tinymce/plugins/wpview/plugin.min.js, wp-includes/js/tinymce/plugins/wpview/plugin.js, wp-includes/js/media-grid.min.js, wp-includes/session.php

Can anyone help?

Thanks
Campbell