First off, I admit I didn't read the previous posts in detail, so I apologize in advance if this has been brought up already.
Ballooning is usually caused by the misjudge of the sink rate of the aircraft. The pilot, probably not looking far enough down the runway, thought the plane was sinking faster than it actually was, thus applied more back pressure than needed, so the plane ballooned.
Trimming of the aircraft to the desire approach speed is important, as it would reduce the pilot's workload in round-out as well as flaring.
Also, knowing where to look during the flare is important. The rule of thumb I use is to look about 8 times the approach speed, in feet, down the runway. In a Cessna 172, where the approach speed is 65kts, I would look about 500 feet down the runway. In a Cirrus, with an approach speed of 85kts, I would look about 700 feet down the runway.
Of course, looking too far down would cause misjudge of the sink rate (too slow instead of too fast) and result in a nose-gear landing.