What kind of malfunction is an "artificial horizon"? I was once (like ten years ago) on a transpacific flight with Northwest from KIX/RJBB to KDTW on a Boeing 747 and our flight as delayed at the gate for about an hour because of some issue with a "floating horizon" (I remembered incorrectly, the issue was a "artificial horizon").

Is that a malfunction with the attitude indicator? What exactly went wrong? It sounded like they fixed it by swapping out a component, maybe the instrument itself?
Best bet is that there was an issue with the artificial horizon. If it was on an older aircraft without a glass cockpit, the gyro or its gimbal was probably broken causing the face to 'float' around or just stick at an odd angle. Then it was then communicated poorly to you by someone. Other than that I have never heard of a "floating horizon" and a google search doesn't yield any results either.