Looks like it could be an SQL issue, may be a corrupted upgrade?
Whenever you upgrade a FO system, other than replacing the source code, one also has to upgrade the SQL database by running:
php FENG_ROOT/public/upgrade/console.php
On the other hand, if you wish to see what is the error message, and solve the issue even faster, I suggest you to change the 'DEBUG' from 'false' to 'true' in the config.php file so that you can know what is going on. Then, you can change it back.
Best regards,
Francisco