Concrete 5 Install Trouble Shooting

We have uploaded the latest version of Concrete5 to our test site and are having an issue with a PATH_INFO error on the initial loading of the installation process on the [login to view URL] page. This is the only issue that is erroring: Support for C5 Request URLs Concrete cannot parse the PATH_INFO or ORIG_PATH_INFO information provided by your server. We need somone to troubleshoot this error urgently so that we can crack on with testing the software to see if it fits our requirements. The server is running Plesk Paralells 10.2 and everything inc the sql dbase is set up ready.