The download file that provides extra content (including the Encore library) has been a big problem in CS6. As of today (and I don't know how much earlier), the main links (e.g. http://helpx.adobe.com/encore/using/download-library-content.html) are still there, but the actual file downloads get a 404 error.
I think the problem is that these were hosted on blog accounts, and somebody changed something somewhere.
There are a couple threads active in the Encore forum, so Encore staff may pick that up. But I don't think they actually control the accounts that have the files. I suspect a helpful Premiere side staff person may have an idea or two.
