aristotle - 4:15 pm on Apr 20, 2012 (gmt 0)
It might look a little "suspicious" to Goog;e's algorithm to get a number of high-powered backlinks over a short period of time. So it might have dropped your rankings temporarily while it "digests" the new information. Your site might come back even stronger after the new links get accepted as genuine.
Maybe you could keep us up informed on what happens during the next few days.