The google pagerank started to update on 9th January 2007 — It was around 3 months and 10 days after the previous update which took place on 29th September 2006.

The update is still going on and you can still find pagerank changes if you are lucky and still got none
I myself got some PR hike today only for 2 of my sites.

For checking this pagerank update , you need to use live pageranking checking tools and not the static tools.

Use following tools :

http://livepr.ezer.com/
http://livepr.raketforskning.com/

Enjoy and Best of luck..