Yeah, I'm no longer signed in to any Apple services on this computer, and I've restarted several times but the issue recurs. Sometimes it works fine. Other times the pref panes just take ages to load. Other times, System Preferences goes unresponsive and the affected panes won't load until after a reboot.
I also tried deleting com.apple.systemprefs.plist and rebooting to see if it helped to have the system rebuild that file, but no dice.
If I have to do a fresh install again, I will I just hope it doesn't come to that.