Default permitted_uri_chars msg not showing up, instead showing exception error msg

Thanks for the reply.No, I haven't tried with a clean version of CI, because the current website is quite a big one and replicating each and every functionality in the new one would be quite a task. As a last resort, i may try this one.

You don't need to redo all your functionality. It's just a test to see if it's a server configuration or PHP version related. If that one works it's not the CI version itself but a combination of your code and CI.