unofficial? could be part of the problem...
I don't think there is an "official" version.
You'd probably be better off to pick up the Etch installer.
Only issue there is that the AMD64 release is currently in the process of moving from temporary development repos into the official Debian ones. Sid is now completely moved to official repos, but I'm not sure about Etch.
I would recommend getting Etch installed, then check to make sure your sources.list is accessing official repos. If it's not, change it and do a dist-upgrade to Sid. Then you can change the sources.list back to 'testing', and by the time you need to update again, things should be worked out.