This is simply a rolling window of 30 days. So, once you extend past 30 days from your 50th most recent question, then you'll be able to ask a new question. Then, of course, you'll be blocked again until the next rollover.
As such, my original prediction was that you'd be able to post today, as this would be 30 days from your 50th most recent question on your profile. However, as you've noticed, this isn't the case, and the reason is because deleted and closed questions are taken into account for the rolling count.
After inquiring with the helpful Rebecca Chernoff I was informed that you actually have 7 deleted questions in your real 50 most recent questions. This would put your next question date to no later than May 11th, 2011. Your 43rd most recent question was on April 11th, 2011, so combinations of deleted question timestamps can only put your 50th most recent as earlier than that, not possibly later.