Error message when in my dashboard

I am getting this error message sometimes when I'm in my dashboard: "A valid URL was not provided." This happens not only in my super-admin dashboard, but also in the user sites. It occurs when I try to do some tasks while in the dashboard. For example, sometimes it occurs when I try to create a new page or post. It just occurred again a minute ago when I was configuring the settings for the Prosites plugin.

This started happening after I attempted to "fix" my multisite database (which is a long story). The short version is that I had used a security plugin (WP Better Security)to replace the database table prefixes (wp_) to a random prefix. I then found out that at least one of the WPMU plugins (New Blog Sites plugin) did not work with the new prefix setup. In fact, when I tried to use this plugin, my entire mulitsite was crashed.

I have since tried to revert my database tables back to the default prefix. Ever since I did this, I now get this error message ("A valid URL was not provided")sometimes, but not always. Right now, I cannot continue with "Save Changes" with the Prosites settings.

Any ideas on how to fix?