I'm running Windows 7 Ultimate 64 and when I run the install package, it checks for file integrity, completes and then does nothing. If I skip the check, still nothing happens. UAC is off and if I try and run as administrator, it just hangs and doesn't even start the integrity check.

Any ideas?Ha, no worries, shortly after I posted the message, the installer kicked in, it's just taken a flipping age to start for some reason!

I had the same problem. After I redownloaded the game this problem disappeared.
Also I had problem to download correct file. Several times the file were corrupted.
I downloaded with Reget and it helped.