I believe the weakness this morning is attributable to an article in the WSJ on Puerto Rico munis trading to yield nearly 10% at year-end. It's old news but still disturbing.
Of course, both Ambac and Assured are in the same boat as to exposure but for some reason it is always MBIA that gets crunched the most. The article points to a possible sale of new PR bonds in the first half of 2014. That will be interesting if not problematic.