I have the same problem as Fenwick. After finishing the first adventure with Merisiel and Kyra, I had acquired a few extra cards (two of them as rewards for success), and now I cannot proceed because there is no means to discard the excess to stay within the permissible deck limits. You try to drag them to the lower section, but they don't "stick". Also, that area usually shows the unassigned cards, but nothing appears there, which seems like a related bug.