FWIW I noticed the same thing today as an MVP, and I have a feeling its related to my lovely rant yesterday about not being able to select More Legroom seats without paying $$.

The entire PC cabin is X'ed out on all of my upcoming flights (i.e. I can't purchase it even if I wanted to), and the same goes for More Legroom seats on applicable aircraft. I would hope that it involves Alaska IT getting to the bottom of the glitch I was ranting about yesterday, but with the way things have gone lately who knows....