I am having the same error I'm using the 64bit version on windows 8.1 and I also tried the 32bit version, and yes I ran as administrator and used the newest client in a diferent folder.
EDIT: I figured it out, the issue is coming from the firewall or the anti-virus. So disable your anti-virus when you are launching PRO or add the .exe to your anti-viru's exeptions list.