I haven't got a fix for this yet but I do have a work around..... use another Mac.
Oh wait; you haven't got another mac. Well this is what I had to do to get around it on the one it wasn't working on.
The problem seems to be that Apple don't like my particular ProductBuildVersion, which is 13A3017. I've got one of the brand new MacBook Pro 15" Retinas released Oct 2013. I'm not sure if that build version is just for these, or just for retina ones or what.
But anyway,
Use this command in terminal
sudo nano /System/Library/CoreServices/SystemVersion.plist
change the ProductBuildVersion from 13A3017 to 13A603 (which is another Mavericks buildVersion)
Archive the app again, (I also restarted Xcode), and resubmit it.
When you're done switch the version straight back to what it was before or anything could happen.
I've submitted a bug report to Apple so hopefully this should be fixed soon.