Prueba con este ligero cambio:
Código PHP:
_root.onEnterFrame = function() {
var myDate:Date = new Date();
if (myDate.getHours()<12) {
mchoras._rotation = myDate.getHours()*30+myDate.getMinutes()/2;
} else {
mchoras._rotation = (myDate.getHours()-12)*30+myDate.getMinutes()/2;
}
mcminutos._rotation = myDate.getMinutes()*6+myDate.getSeconds()/10;
mcsegundos._rotation = myDate.getSeconds()*6;
};