One thing to keep in mind is that the only thing that’s updating right now is ‘visible’ PR; Google has a running PR on their backend that affects your SERP’s. They’re not making it visible or current through their toolbar for the same reason they’re not showing accurate backlinks: to block attempts to manipulate their SERP’s.
i.e., just because the toolbar says a site has a PR of 1 doesn’t mean that the site has a PR of 1 right now. It means it had a PR of 1 last time Google updated their display.