I think the problem may have been a plugin that grabbed other posts from another WordPress blog (that is on the same domain but not same WordPress instance) and inserted those posts into a site on the current multisite instance that is screwed up.
For the record, the first trouble-shooting step should always be to deactivate your plugins. If your site was running slow before, merely updating isn’t a fix. Figure out what’s breaking first.
I say this because now you have two problems:
- You’re still having slow page loads
- The update to WP 3.2.1 broke something in your installation.
What would be my best course of action? I do have a copy of the DB pre update as well as a copy of all WordPress files. The thing I thought to do was to revert back to 3.19 and export each site, start with a fresh install of 3.2.1 and then import each site.
The safest plan of action is to wipe everything and restore back to where you started with your backups. Get back to where you were before the update … then take some time to figure out what’s causing the slowdown.
I recommend setting WP_DEBUG to true, installing the Debug Bar plugin (so you can track query activity), and working your way through your plugins until you figure out what’s causing the initial issue.
Once you’ve solved that problem, and no sooner, you should update to WP 3.2.1.