Feature '6b744ecb-82fc-4896-a981-1ad8dc5c47c2' for list template '10000' is not installed in this farm.
I had to check and it only affected one site - not happy about the time I spent on it but it appears that one app had installed a new List using that ID. Deleted the list and emptied the recycle bin. Returned to the site and it Crashed! It actually took a reboot to fix.
You be careful out there!