Extensive thread from last year.
http://www.pprune.org/archive/index.php/t-385214.html
From PJ2.
I learned later that it was a known issue by Airbus and that another large US carrier had had experience and it was even written up in Airbus' larger "industry issues" publications they used to distribute. Why our maintenance people or flight ops people had so much trouble finding out what it was, was a mystery. The fix was as stated here - replace worn elevator bushings, and, using a special tool, bias the elevators "down" by half a degree (if I recall). The fleet problem disappeared overnight.