There's a nasty, elusive bug going around that doesn't properly tell the region that its Lord is gone when the Lord dies under some circumstances.
We fixed it twice a couple months ago, but apparently we need to fix it more times.
Unfortunately, I don't have time to go brogging about to figure out where it's still happening today, but hopefully I should have some more time in the next few days.
Either way, I've nulled out the offending fields in the database, so the immediate issue should be fixed. Please keep us updated.