I have recently gone through many discussions about page rank n/a for all the websites. even I have read somewhere "Google has suspended PR in regard to pay tribute to Steve Jobs" :confused: What Steve jobs have to do with Page Rank:confused:
Neways, i also experienced the same problem in the afternoon while working, SEObook toolbar was not showing PR for any of the websites.. I simply switched to Google Toolbar. I thought might be problem with my firefox as i just updated it today.
So don't panic PR is still there and is the same as it was in the morning.. Simply go to toolbar.google.com and get the toolbar installed. Now Chill
PS: R.I.P Steve Jobs.