I was interested in this thread because I launched a blog at the end of March and was wondering when the page rank would ever change. Now, I see that I have a long time to wait.
It will generally take 2-3 months get a PR for new site. But there may some rare cause like you describe.
I'm going to replicate this for a personal experiment with a couple of new domains I've just purchased so I'll let you know how it goes and report back those findings in about 3-6 months... It'll probably be after the 4th quarter PR update so we'll see if this works. Cheers good people
Update: I wasn't expecting an update so soon but the PR for the new site is gone, down to zero, and all but one of the 40+ links to it are also gone! I've checked a few tools and they're all reporting the same so that was interesting and short-lived!