How to import iChat/Messages chat logs/history?

I had to restore my system from a month-old TimeMachine backup to a new drive yesterday, but still have access to my old hard drive. My newly-restored boot drive now has chat logs up to a month ago, but my previous disk still has yesterday's log (though mysteriously, it has lost everything inbetween... but I digress).

I have already moved yesterday's archive folder out of the old ~/Library/Messages/Archive folder and into the one on my new boot drive. But Messages on my new boot drive simply refuses to see it. Not only that, but any chat I click in Messages now, "slides" down the list of chats, and all content disappears - even the last message normally displayed in the sidebar disappears.

How can I get my chat history to be seen in Messages again? I use it on my iMac (primary machine), a MBP, an iPhone 4s, and an iPad3 and have always loved that they all just worked seamlessly and were in sync. How can I get that state back?

Or another way to think of it, is there a way to restore Messages on my iMac, from what's stored on iCloud? My iDevices still both have the complete history of all my chats, so I would think there would be a way to restore them to my iMac, but have yet to find it.