Its not confirmed news, but after Caffeine update, its might be in motion. Last update was around February, 2009. Its already about 7 Month, Means 210+ Day.
And main reason is we are sensing some change in PR among BlogSpot Blog. We generally know BlogSpot blog got PR update frequently then sites. But Depending on few source and community feedback BlogSpot Blog’s PR changing. Most possibility is Google Changing some algorithm, they might be considering Yahoo LinkBack with more priority.
So People fasten your set-belt, PR update might come in 24-72 Hr. And might last time, for sometime all PR server might starts to fail and showing 0 PR for most site. Just dont worry. Exact PR will come to your site in time.

BTW i Think Best PR checking Site is – http://LinkX.In/pr