by Emma Richardson.
Ken is right, turn debugging on and see if anything shows up.
I really suspect that something corrupted in the migration. You might start by redownloading the version of moodle that you are on and replacing your moodle code folder with the newly downloaded one. You will need to copy across all of your plugins and your config.php file. Then, make sure that you get the ownership and permission applied recursively on the moodle code folder and see if that does not resolve a lot of it.