Yes, with WP 3.9.1, the plug-in causes the blog to display just a white screen (the WP stupidity that is supposed to indicate to the end user, among a gazillion other things) “Problem instantiating plug-ins”.
I suppose no one at WP has ever heard of try/catch blocks?
Anyway, this plug-in is attempting to load:
/wp-includes/js/tinymce/plugins/spellchecker/…
which does not/no longer exists.
After hacking the database and disabling this plug-in, WP comes back online. Alternatively, you could remove the plugin’s sub-folder from wp-content/plugins/.
This plug-in should be removed from the WP site (or updated to work with 3.9.1).