If you hover your mouse cursor over a card on the combat map, it raises up. If your mouse cursor would then be in the vacated space below it, the card loses mouse focus, and falls back in place. As soon as it falls back in place, the card regains mouse focus, and the process repeats. This causes an epileptic seizure inducing twitch. =)
Right to the end of the FAQ: http://www.cardhunter.com/forum/threads/frequently-asked-questions.2160/
Um. Of course it is. I swear, the FAQ is the one place I didn't search for a known issue before posting. =( Looked in all the other issue threads... Thanks! There seriously needs to be thread edit controls.