Hi, I am getting the following error message when I install C5 v 5.7.5.3 on my system:

An unexpected error occurred.
Can't inherit abstract function Concrete\Core\Validator\ValidatorInterface::isValid() (previously declared abstract in Concrete\Core\Validator\ValidatorManagerInterface)

Does anyone know what this means or what might be causing it? I've installed this version of C5 for other sites without any problems.

Any suggestions would be appreciated!