Another workaround, 'til it gets fixed... :|
When the ad fails to load in CTTH play, the "ad area" at the bottom of the scorecard screen goes blank. I use this as a "cue" to click the "Replay" button... then exit the replay by clicking the "Exit" button.
This forces another (presumably different) ad to load in that same "ad area". Then by clicking the "Continue" button, the "black box" doesn't have a chance to "manifest itself".
Never had it happen twice in the same CTTH round, yet. I'm using Comodo Dragon with no adblocks active.