I posted about something very similar yesterday... My site had about 10 of it's main pages go from PR6 to PR1 when the PR update occured near the first of April... Now my site has over 1,200,000 inbound links, and I KNOW it wasn't because I lost links... Yet my rankings ALL stayed the same or improved... so did traffic. Here is the post:
i appreciate the post of encouragement.. it's the first time i've ever seen a PR of 0 on anything i own... very scary stuff. I will give it a day or two and see what is going on.
I agree with Have u checked the PR on other sites ? Check it on many sites before taking any conclusion ..
my PR went up a place, after site update, then a few weeks later went down again 1 place, how strange.
My article directory site went from pr3 to pr0, I was assuming its because ive been accepting any shitty old PLR articles and googled slapped it down for duplicate content. I was gona give it a few weeks to see if it recovered. But wasnt to bothered as its not really one of my main sites.
it was a PR5. we use the htaccess hack to keep from duplicate content, it's all unique content added by users (big site) and has three revenue streams including adsense, TLA and affiliate programs.