Why are platforms unavailable for migrate or clone?

Hello, I've got a neat setup for development where I have an Aegir master virtual machine on my development workstation. When a site is ready to go live I will migrate it out to my Aegir Remote/Live server on the web. This works very well for me because the platform remains in-tact on my VM box, and Aegir just mirrors the platform and site out to the remote and puts the site database on the remote instance, I've been very happy with this setup so far.

I've run in to a issue tonight that I don't know how to fix, or what is causing it?

-- Issue: when I try to clone or migrate a site from the Aegir Remote to back to my Aegir Master/Dev box - some of the platforms are grayed out/the radio buttons are not selectable. This does not seem to be the case when I want to migrate or clone any local/Master site out to the Remote, it's only happening from the Remote to Master.

Can someone explain what causes platforms to not be available? I have explicitly "locked" two platforms that I no longer use, and those are understandably not selectable, but I don't understand why the other platforms are not? As well all of my platform names and sites are unique with dates added on the end so the namespace won't conflict.

Thank you, --Tony