I recently had my site updated to version 184.108.40.206 and now there is a bar across the top saying
"Class Rewrites cache is disabled. It is strongly recommended to turn it on! Do not turn it off except for development purposes! Click here to go to Cache Management and enable Class Rewrites cache."
However when I got to Cache Management I don't see any option to turn this on. I've searched a bit using google and can't find much. Any have any ideas where I can start on this one?
It my be left by the custom extension.
Seems like you have disabled/deleted part of it which display cache option.
Also please check if it useful for you: http://www.aitoc.com/en/blog/no-rewrites.html