The last update i heard was the Google Panda update after that the search engine give more preference to unique content. Google now shows all pages of sites when search for core keyword. Search "Google" then you will find the new search result pages, actually it concentrate on the brand name.
yes the PR toolbar was updated yesterday. Just keep building links and content. Hopefully your PR will bounce back next update.
Whats the emergency? Google has updated the PR, some goes high and some lean. If your PR gets lowered then you need to build more and more quality backlinks so that it goes up in the next update.