Ann: Quarterly Activities Report , page-21

"Mine development continued at an aggressive rate during the quarter with record mine production of 151,412 tonnes at an average grade of 3.56g/t Au from the Tindals Underground Mine, including production of 60,300 tonnes at 4.8g/t for the month of December - well above the targeted monthly average of 45,000 tonnes for 2011."

That would explain the higher production costs, they are mining well above the targeted monthly average, translates as more costs more than budgeted per month too. Mining it faster than milling and selling it, explains their increase in bullion also.