404 error when activating prosites plugin

This may be an issue solely related to weird hacked together install I am using. But, today I was troubleshooting some stuff and deactivated all my plugins. In the process of going through to find my conflict, Prosites wouldn't reactivate for me.

Everytime I tried activating it, I got a 404 error. After a bunch of research, I got no where.

I stumbled upon this guidance about error logging from another website and used that to see if I could gain some inside.

Lo and behold, after much struggling, the first time I tried to reactivate the plugin after added that code, it worked. I didn't get the 404 error, but the error logging added this to my error log:

[04-Nov-2013 01:26:02 UTC] WordPress database error Multiple primary key defined for query ALTER TABLE wp_pro_sites ADD PRIMARY KEY (blog_ID) made by require('wp-admin/plugins.php'), activate_plugin, do_action('activate_pro-sites/pro-sites.php'), call_user_func_array, ProSites->install, dbDelta

I don't know what it means, and I've got Pro Sites, but is it important and should I be worried?