Recheck your tilesets. If it only happens on your beach tileset, maybe the setup is different than the others.
@Ryex: Yes, that's it. Everybody goes from everything passable to impassable while I do it the other way. That way I prevent many passability problems. If something is impassable, I'll definitely find that bug while finding something that is passable, but shouldn't be, is a pain in the ass. >.<