This is common, Google is messing with the algo's again, stop looking at the
PR crack, because it means nothing, all that matters is traffic.
Are you still ranked in the right places
Did you lose any positions in the organic listings
This is what I would worry about, this whole
PR thing is just a ego trip. Google should of never released this to the public, the internet would be better off.
You wouldn't be asking this question, you would continue on with doing what your suppose to do instead of looking at this
PR crack.
Give your visitors value and you will be rewarded.
Ed