Game ID: #3478748
It appears that ending your turn with more Scheme topdecks available than action cards in play causes the game to freeze, not allowing you to either select cards to topdeck, or even just end your turn.
Yep, that's right and we agree on the probable root cause as well. See http://forum.shuffleit.nl/index.php?topic=1480
Makes sense, figured I'd post again since it wasn't listed in the known bugs, nor had there been responses in the past 2 months on that post.