Odd interaction with two cards that was unresolvable.

[uacrobi]

We were playing a 5 way game that we generated random decks for. One player played Invasion Plans. The other played and activated War Cadence targeting the one player who only had that creature. Both players were tapped out. The attacking player was unable to proceed because War Cadence was forcing him to choose that creature as a blocker, when he picked it, xmage said the attacking player needed to pay 1 to declare the blocker, even though it wasn't HIS creature. Xmage did not pick up that there was a can and can't effect for blocking, and can't always wins. It would not let us proceed, we had to roll back and NOT activate the Cadence.