Issue with Site

I have had a site running CMS 2.05 for some time and it had been running fine. Until today that is when I enter the site url I get

"Error: You must install the program before you can use the viewers." and when I try to access the admin panel, I get

There doesn't seem to be a problem with the

"Fatal error: Call to undefined function renameorremovedefaultfiles() in /home/uhurupeace/X4E58G7S/htdocs/cmsAdmin/lib/admin_functions.php on line 39

There doesn't seem to be a problem with the server as I have other instances of CMS builder running on it (on different domains)

Has anyone got any ideas,

Thanks