Something weird is going on, that is for sure. One of my blogs seem to have lost its PR but when I use a PR checker tool, it still has its PR2. Very weird!
Google is on updating its index. An updated is ongoing "Caffeine Update". Google is making SERPs more sophisticated.. its kind of infrastructure change. For last six months Googlers are on the process. They have almost finished the change but updating it gradually. After some time you will find great change in the SERPs. So far i observed in this updates they have updated most of their algos.
I just picked up another Client and his whole site is a Pagerank 4, every page. Of course my link with keyword went on the bottom of every page. 10 Pagerank 4 links in one shot. I love this business.
I just had a lot of pages (about 20) go from PR N/A up to PR5. But.. these pages were PR5 for about 2 years, and dropped about a month ago so it looks like it was a correction to fix it and not any widespread update.