On any option that required my pressing the "X" key, the button refused to appear -- playing pet games, speaking with NPCs, picking up items, and so on. The problem was confined to a single character.
Oddly enough, shortly after I posted, the problem disappeared. It later appeared on another character, but only briefly. Now all seems well
My sister tells me this problem occurs from time to time.
I know you are uninterested in this, but I began playing Wizard 101 to spend time with my sister's darling children, and found it more addictive than I would have thought possible. We they grow up, I shall be forced to find some other excuse for my addiction to a child's online game.