Matt Cutts just confirmed that Google has updated PageRank values that are displayed on the Google Toolbar.

CNN.com is now part of the elite Google PageRank 10 club while both Twitter.com and WordPress.com domains have climbed to Level 9.

http://www.labnol.org/internet/google-toolbar-pagerank-updated/6293/

The last time was in April, or was the algorithm changed during the summer time?
April change here:
http://blogoscoped.com/forum/129966.html

I googled now and it appears that there was an update in October too.