I am, by far, NOT a SQL guru. That being said, I can't determine what's broke to even begin to troubleshoot/fix it.
The Linux server that this affects was completely overhauled, and subsequently got a MySQL server upgrade. I've copied /var/lib/mysql from the old drive in its entirety, but... the sites that use PHP to query MySQL databases via links, nothing happens when I click a query link; it just seems to reload the page. Why? Well, I suppose it's because it's not able to connect to the database to generate the query, right? However, it's not outputting any errors to the browser on any of these sites.
I believe that I've probably overlooked something, and any shove in the right direction would be great!