If you are worried about your PageRank number, your priorities are off. Be worried about your actual search traffic. If that has not dropped off, there is not cause for concern.
As far as advice goes, I'll stick with the default white hat advice: Improve your search traffic by building as much good original content you can and form relationships with other quality relevant sites that lead to backlinks.
As a result of the PageRank drop, the search traffic dropped by 35% - which is huge.