User blog comment:Otakon7/Otakon7's Buddyfight Simulator/@comment-24547588-20140502160209/@comment-2234004-20140502161738

It says you tried to create a deck whose name already exists.

If you update a deck, you must use "Save Changes", what you clicked was "Save as New" (I can tell since I see the deck name in the Info box behind)