Clarence - 4:05 am on Oct 28, 2012 (gmt 0)
This is a Google Split Test. Google is trying to see which ad look and feel performs best. Google does these test all the time, and if the test show that the new ad look and feel doesn't increase CTR they will go back to the old look and feel.
I have seen these test a lot, and in the short term your earning do suffer. If you're using an adserver like Google DFP switch to a different size unit that isn't being tested.