Hi all, I'm trying to install OS X onto an old Mac Pro using Sierra. When I get to the end of the installation, I get that dreaded error message "Package failed signature validation check" or whatever bollocks it is. I've checked the time and it's correct, I've used ntpdate to sync the clock correctly from the installer and I still get that message. Does anyone else have any tricks that I can use to get past this problem? (Used 10.11 and got a different error, fortunately this was at the BEGINNING of the install process) Thanks!