Sometimes, when running the "Check PAD files for updates" routine, CT will fail to check some of them, While sometimes the file is indeed missing (the website has been suspended, the site still exists but the PAD is no longer there), in other cases, the PAD file is clearly there and yet it fails to process it. Of course, you are given the option to "delete it or process it later", but in some cases, once it's failed the check, it becomes "blacklisted" and every subsequent check will fail.
One such example is this:  http://www.atp-inc.net/Packages/Xml/sftpcf.xml This one worked fine and then one day it got the "curse", and since then, it constantly fails verification, even though it's still there on the remote server (I've checked every time I ran the "check for PAD updates" routine).
There seems to be no way to remove the blacklist. The only way is to remove the record completely, and if I do that I lose the download count and the subscribers.