I have downloaded and installed C5 and followed the instructions to the letter and my host company have overseen this also. However on going to the URL I get the following error message and am at a loss to know what this is and how to resolve the issue and get started with C5... HELP

Fatal error: Class 'Zend_Cache' not found in /usr/local/psa/home/vhosts/ugolfmedia.co.uk/httpdocs/concrete/libraries/cache.php on line 52