Here are a few threads to read on the recent update in toolbar
PR:
Google's PageRank Update Goes After Paid Links?
Source: Google PageRank Update October 2007 | Andy Beard - Niche Marketing
Google Drops PageRank For Many Sites : Paid Links or New Algorithm?
SEOmoz | Google Toolbar PageRank Losses For Hundreds of Websites
Top Websites Lose TBPR….Um Who Cares? - Jaan’s Search Marketing and SEO Blog from Cincinnati, Ohio
Google's Paid-link Smack in the Face - Search Engine Guide Blog
I really don't feel the drop is related to the current update. 11% percent is really not that much and could be one or many reasons for it:
1. If your URLs changed in the recent revamp, did you 301 redirect the old to to the new? if not that could be the reason in its self.
2. Competition is ranking better
3. Weather, world events? You target California, maybe the recent fires have something to do with it?
4. Maybe the niche your in is simply not getting as much traffic as it did last year.
5. Customers buying less in your niche.
6. Content changes during revamp?