So I'm playing Bookworm and I finally get it worked out so that I have EXHIBITIONER spelled out with plenty of those primo jeweled tiles to really rack up the score. Figuring I have it in the bag, I move tiles until I have an S to make it EXHIBITIONERS...except when I go to click that final tile, a big red X appears over it and it's refused!

So I guess the limit is 12 letters. Anyone else run into this?