Can't add new AddOns!

[Wowk]

I have several Addons, all of which are working ok. I recently downloaded the latest update to Flightmap, which I had used in the past with no problems. But it doesn't show up as a button in my Addon page. As an experiment, I downloaded another small Addon, and it also doesn't show up. I tried moving all of the Addon files to my desktop, deleting the Addon folder in the WoW Interface, creating a new one, and moving things back. My old addons still show up, but not Flightmap.
I have Windows XP. I did the usual routine- downloaded the file, extracted the files using the Windows extraction tool, and moved the Flightmap folder to my Addon folder (exactly like I have done many times). So why can't I see Flightmap, or the other new Addon?