Updated to r422, can’t find any installer discs

So, I updated to r422 today, and instaup2date errors out every time when trying to find the installer disk. The disk I'm trying to use is a 10.6.6 disk, which I have just imported today, and I've added the build number to my catalog file. Did something change with the way I have to declare which disk to use? I don't recall having to do this with a previous revision... Any help appreciated!